Correct Answer: (2) 2:1

Correct Answer: (3) These types of plants make food at the fastest rates with red and blue light.

Photosynthesis is the process of converting carbon dioxide and water into glucose (food) and oxygen by the use of light energy. The bubbles counted represent the oxygen formed. Thus, more bubbles would also mean more food produced because they are both products of photosynthesis. Based on the table, red and blue lights generated the most number of oxygen bubbles in the 30-second periods.

Incorrect Answer:

Yellow and green light did not carry on photosynthesis well because they only generated 11 bubbles or fewer in all the plant species tested.

All the plants exhibited faster bubble formation when blue light was used, followed by the red light.

Water did not filter out the red and blue lights because if that is so, then there would be no photosynthesis that occurred.

Correct Answer: (3) temperature of water

The independent variable is the variable being manipulated or changed and the dependent variable is the observed outcome of the independent variable being manipulated.

The heart rate of the water fleas increases as the temperature of the water increases. The heart rate and temperature are directly proportional with each other.

Correct Answer: Temperature or pH

Enzymes are proteins that serve as catalysts in biological reactions. Catalysts are chemical agents that change the rate of reaction without being consumed during the process. These enzymes work only at a certain temperatures and pH levels.

Centrifugation is a procedure that involves the application of the centrifugal force for the separation of mixtures, often used in the laboratory. More-dense components of the mixture move away from the axis of the centrifuge, while less-dense components of the mixture move towards the axis. The effective gravitational force may be increased on a test tube so as to for faster formation of precipitate ("pellet") at the bottom of the tube. The left over solution is called the supernate or supernatant liquid. The supernatant liquid is then either quickly decanted from the tube without unsettling the precipitate, or sucked out with a Pasteur pipette.

This study aims to know if regular exercise could improve the left part of the brain which is responsible for processing mathematical problems. A large number of individuals will be tested to deduce a more credible result and to decrease the margin of error of the experiment.

The experimental and the control group will be asked to solve mathematical problems. Their scores and answering time will be recorded. Then, the experimental group will exercise for 15 minutes everyday for 21 days (most studies claim that it takes 21 days for the brain to recognize an activity to be a habit). After 21 days, both groups will solve mathematical problems. The scores and the answering time will be recorded. The scores and the answering time before and after 21 days will be compared in both groups. If the experimental group answered the exams faster (with almost the same score before and after the 21 exercise days) after the 21 days, and the control group did not improve in their answering time, then it can be concluded that regular exercise improves the mental performance of humans.

Correct Answer: (1)

Pulse rate is the rate of the heart beat. It is measured by the number of beats per minute. Pulse rate is affected by the activities of muscles of the body. The more vigorous the movement, the more blood is needed to supply oxygen and energy to the muscles, and thus, the faster the pulse rate. Among the four activities performed by the student, watching TV (A) required the least movement by the body. It is followed by talking while sitting down (D), then walking going to his friend's house (B). The most vigorous activity he did was running to the mall (C), and therefore the highest pulse rate was recorded.

Correct Answer: (2) The red blood cells will lose water and decrease in size.

Osmosis is the diffusion of water across a selectively permeable membrane depending in the concentration of the solutes on either side of the membrane. The water moves from an area on low solute concentration to an area with high solute concentration. In the case of the red blood cells, since it has lower salt concentration, the water will move out of the cell and thus the cell will decrease in size.