Consider the experimental situation described below. Ability to grow in shade may help pines in the dry forests of Arizona resist drought. How well do these pines grow in shade? Investigators planted pine seedlings in a greenhouse in either full light or light reduced to 5% of normal by shade cloth. At the end of the study, they dried the young trees and weighed them. Identify the experimental unit(s) or subject(s)?

a) shade cloth

b) pine tree seedlings

c) drought resistance

d) greenhouses

e) rainy seasons

The experimental subjects are pine tree seedlings .

Step-by-step explanation:

The physical entity to which the treatment is assigned at random is known as experimental unit .  

The same treatment cannot be received by two experimental units, they have to different treatments. The selection of experimental units plays an important role to determine the p-values in the statistical analysis. The experimental units are divided into different homogeneous groups called blocks.

From the question, the experimental subjects identified are pine tree seedlings.