Question

Which sentence contains an essential adjective clause?

The coach explained the rules that the officials revised in 2010
The coach, an expert in the sport, explained the revised rules to us.
After explaining the rules to us, the coach released us to the field
The officials revised the rules, which the coach explained to us before practice.

Answer 1

An essential clause does not require commas. Having this in mind, there is only one sentence here that is not separated by commas, so the correct answer is A. The coach explained the rules that the officials revised in 2010.