Correct Answer: Option 2 90mm

Approximation or estimation typically means finding upper or lower bounds of a quantity that cannot readily be computed precisely and is also an educated guess. Since we are limited by the ruler, we will just estimate the length of the earthworm based on the number of centimeters covered. One centimeter is composed of 10 millimeters. Based on the diagram, the earthworm covered 9cm which is equal to 90mm.

Based on the results of the experiment, the higher the temperature, the faster is the rate of gas production. After 25 minutes, the 35^oC setup yielded more bubbles than the 20^oC setup.

The product of the respiration process is carbon dioxide and water. Thus, the gas in the bubbles formed is carbon dioxide.

Hypothesis: Reduced amount of living space in between plants would slow down the growth of plants.

Aside from the plant size, the same species of plant should have been used.

The dependent variable in this experiment is the number of plants in each pot. This variable determines the height of the plants.

The data supports the hypothesis that reduced space in between plants would slow down growth. Results showed that as the number of plants in each pot increases, the average daily plant height becomes lesser. The reason behind this is the amount of nutrients that will be used up by the plants. The higher the number of plants, the more nutrients is needed for growth and development.

Correct Answer: Option 2 Two sets of clothespins, one that is easy to open and one that is more difficult to open.

This is not necessary because the clothespin should be control. Changing the type of clothespin will affect the results.

Options 1, 3, and 4 are necessary for the experiment to be significant. The hypothesis will guide the researchers during experimentation. A small number of students is not enough to prove the hypothesis. Control ad experimental groups are needed to arrive at a relevant conclusion.

Correct Answer: Option 2 It shows the effect of a dependent variable on an independent variable.

Controlled experiment generally compares the results obtained from an experimental

sample against a control sample, which is practically identical to the experimental sample except for the one aspect whose effect is being tested (the independent variable).

Correct Answer: Option 2 separating DNA fragments on the basis of size.

Agarose gel electrophoresis separates DNA fragments according to their size. Typically, a DNA molecule is digested with restriction enzymes, and the agarose gel electrophoresis is used as a diagnostic tool to visualize the fragments. An electric current is used to move the DNA molecules across an agarose gel, which is a polysaccharide matrix that functions as a sort of sieve to help "catch" the molecules as they are transported by the electric current.