alternative

Here is a sentence from my homework at school:
" I travel by bus only when I have no alternative
a. I travel by bus only as a last resort
b. Travelling by bus is my only alternative
I chose b but my teacher chose a, why?👁 Frown :(

Hi screenactorsguild, I'm assuming the answer you need to choose should paraphrase the original sentence. Is this the case? If so, a is correct, because the original sentence states that you only travel by bus when there is no other alternative, meaning that it is the last option you choose. You only take the bus when no other method of transport is feasible, thus making it your last resort, as option a) states. If you were to say that travelling by bus is your only alternative, you would be saying that travelling by bus is your only option or the only other method of transport available as an alternative to something else, thus contradicting the original sentence and making option b) incorrect. I hope this explanation helps!