Answer: <span>A reaction progress curve has three peaks and two valleys between the peaks. This curve describes a reaction mechanism that involves
<u>three elementary reactions</u>.
Explanation: I have drawn the progress curve with three peaks and two valleys. In fact the peaks shows higher energy and valleys show lower energies. So, Let suppose we react
A and
B. This reaction between A and B results in the formation of
C. In this reaction the energies of A and B are less, and during the progress of reaction they cross a transition state of higher energy and forms product C with lower energy which is present at lower valley. This was first reaction. Other two reactions will be followed by conversion of C to
D and conversion of D into
E.</span>