Biologists designed an experiment to test the effects of compost on the development of root crops

The crop has good yield because Compost has a good effect on root crops.

Explanation:

Compost has a great effect on the development of root crops such as onion, potato, garlic and ginger etc. Compost provide nutrients to these crops as well as soften the soil due to which they grow rapidly. It also improved ventilation, soil structure and soil texture which is very necessary for the crop. Due to ventilation, oxygen gas is available to the roots which increases growth and yield of these crops. Compost also retain water and nutrients so they are available to the roots. So those plots where compost is applied observed increase in yield as compared to other plots.

the farther away the object is from the central star (the sun) it's gravitainal pull on the object is weaker when it is farther

explanation:

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".