Final answer:
When we need to determine all possible outcomes for a sequence of events, we use counting rules. Therefore, option a is true.
Step-by-step explanation:
a. True
When we need to determine all possible outcomes for a sequence of events, we use counting rules. These counting rules include the multiplication rule, which states that for two independent events, the total number of outcomes is found by multiplying the number of outcomes for each event. The addition rule is used to calculate the number of outcomes when two events are mutually exclusive (have no outcomes in common). Therefore, option a is true.