Question

Which of the following RNA types is involved in protein translation?

Answer 1

All the types are actually involved in some way:

tRNA is part of the molecule attached to the ribosome
mRNA is being translated
rRNA is a component of ribosomes, along with proteins

But tRNA and rRNA cannot function on their own, while mRNA is "used" on its own so I'd rather put mRNA as the main RNA involved in translation.