Final answer:
The expression 3y + 1 is already in its simplest form and cannot be factored further, so the answer is (c) 3y + 1.
Step-by-step explanation:
The student asked to factor the expression 3y + 1 completely. When we look at this expression, it is already in its simplest form because there are no common factors between the terms other than 1, which doesn't change the expression when factored out. Hence, the expression can't be factored any further, and the factored form is the same as the original expression.
The correct answer choice is: (c) 3y + 1.