Final answer:
The correct form is 'volunteers who would like to work the morning shift' because it is a restrictive clause that does not require commas. This clause specifies which volunteers are being addressed. The correct option is b.
Step-by-step explanation:
The correct sentence is b) volunteers who would like to work the morning shift. This is because the clause 'who would like to work the morning shift' is a restrictive clause, providing essential information about the subject 'volunteers.'
A restrictive clause is not set off with commas since it narrows down which particular volunteers are being referred to. Commas are used for non-restrictive clauses, which provide additional information that is not essential to the meaning of the sentence. The correct option is b.