Look at the underlined part of each sentence. Below each sentence, three possible substitutions for the underlined part are given. If one of them (i.e.,) (a), (b) or (c) is better than the underlined part, indicate your response on the Answer Sheet against the corresponding letter (a), (b) or (c). If none of the substitutions improves the sentence, indicate (d) as your response on the Answer Sheet. Thus a 'No improvement' response will be signified by the letter (d)
They set a strong guard, lest anyone $could$ escape