I assume you are intending to say lumens per watt? You first, what do you think? After you answer, we will help. We are not in the business of just answering your test or homework question; however, we are here to help you.
Soory no, it certainly is not MV, HPS has twice the efficient than MV, And some of the new t-5's are better than HPS.
but the most efficient source in general use is low pressure sodium.
Tom,
it's been so long since I've seen a Low Pressure Sodium fixture or lamp. I've known too much since then so they've been almost completly erased from memory
Todd