For a complex reaction the reaction progress curve
a)has several hills and valleys
b)has only one peak
c)is a flat line
d)shows energy vs. pressure

a) has several hills and valleys

Explanation: Elementary reactions are reactions which takes place in one single step and thus contains only a single peak.

Complex reactions are reactions which cannot take place in one step but takes place in a sequence of number of steps.

In a complex chemical reaction, the reactant molecules pass through different transition states due to bond breaking and bond making. Here the species stays for a very short period, usually called transition period of activated complex.

not clear

b

explanation:

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