Answer:
A. He was concentrating hard on his book
Answer:
Example: If you want to explore the effect of salt on a plant growth, the control group would be a set of plants not exposed to salt, while the experimental group would recive the salt treament, so you answer is control group.
So, a possessive noun is usually used to indicate who or what has something, like "The Dogs' ball."
To change this form of children,plural, to a possessive noun, you will want to add an apostrophe, and then an s. It changes to this:
Children's
C. Strive. If an athlete aspires to become a professional, he or she strives to do so.
