Whatever was said next would be crucial, so, in order to make his voice as clear as possible, he coughed a little, but taking care to do this not too loudly as even this might well sound different from the way that a human coughs and he was no longer sure he could judge this for himself.
There are no more uses of "crucial" in the book.
Show samples from other sources
Doing well on the SAT is crucial to getting into the college I want to attend.
The information is crucial to making a good decision.