In tomatoes, red fruit color is dominant, R, to yellow fruit color, r. A farmer has tomatoes that produce either red or yellow tomatoes. He has signed a contract with a large seed company to provide pure, RR, and pure yellow seeds, rr. They do not want any hybrids. How could the farmer tell if his tomatoes are pure or hybrid?

He should perform a "testcross" by crossing the tomatoes in question with yellow-fruited plants.

If they are pure, all offpsring will be Red:  RR x rr = all Rr

If they are hybrids (heterozygous), half the offspring will have yellow fruits:  Rr x rr = 1:1 (red to yellow)

Explanation:

it is either c or d and i know for sure it is not a or b

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.