Final answer:
An element in the activity series can replace any element below it on the list. The activity series is a list of elements in decreasing order of reactivity. It can be used to predict if a reaction will occur. Option b.
Step-by-step explanation:
An element in the activity series can replace any element below it on the list.
The activity series is a list of elements in decreasing order of reactivity. For a single-replacement reaction, a given element is capable of replacing an element that is below it in the activity series. This can be used to predict if a reaction will occur.
For example, if a metal is below another metal in the activity series, it can replace that metal in a reaction. However, it cannot replace a metal that is above it in the activity series. Option b,