单选题 Only five years ago, there ______a shortage of computer specialists.

A、 (A) was
B、 (B) were
C、 (C) has been
D、 (D) have been

【正确答案】 A

【答案解析】The simple past tense is required. Choice (B) is past tense but does not agree with the singular subject shortage. Choice (C) is present perfect. Choice (D) is present perfect and does not agree with shortage.