A gardener wants to try different combinations of fertilizer (none, $1$cup, $2$cups) and mulch (none, wood chips, pine needles, plastic) to determine which combination produces the highest yield for a variety of green beans. He has $60$green-bean plants to use in the experiment. If he wants an equal number of plants to be assigned to each treatment, how many plants will be assigned to each treatment?

a. $1$

b. $3$

c. $4$

d. $5$

e.$12$

We are given some information about an experiment. that includes different combinations of fertilizer (none, $1$cup, $2$cups) and mulch (none, wood chips, pine needles, plastic) to determine which combination produces the highest yield for a variety of green beans. Experiment is conducted on $60$plants. We need to find out plants needed to be assigned to each treatment.

To figure out how many alternative combinations the gardener wishes to try, multiply the number of options in the first set by the number of options in the second set. In our experiment in first set of options we have((none, $1$cup, $2$cups) and second set contains mulch (none, wood chips, pine needles, plastic).

So, Total combinations= $3\times 4=12$

It means we have $12$combinations of fertilizers and mulch. We have $60$plants for experiment.

Number of plants receiving each treatment= $\frac{60}{12}=5$

Hence, option d is correct option.