Which of the following statements holds true for a chemical change?
O A. In a chemical change, no new substance is formed.
OB. In a chemical change, a substance changes its phase.
C.
In a chemical change, the molecular structure of a substance changes.
OD. In a chemical change, one substance dissolves into another.

Option C) In a chemical change, the molecular structure of a substance changes.

Explanation:

Since a chemical change involves the formation of new substances, and is usually irreversible, the molecular structure of the reacting species changes during reaction to form entirely new products.

An example of chemical change is the formation of ammonia from nitrogen and hydrogen gas shown below:

N2(g) + 3H2(g) --> 2NH3(g)

In the above reaction, the molecular structure of N2(g) and 3H2(g) changes to yield a new substance, 2NH3(g).

Thus, in a chemical change, the molecular structure of a substance changes.

answer: they produce more slow than unicellular organisms.