問題補(bǔ)充：
單選題
The bridge is so important to the people here that once ________ it must be carried out without delay.A.designsB.having designedC.designingD.designed
網(wǎng)友答案：
熱心網(wǎng)友 1樓
D解析這里用過去分詞，相當(dāng)于一個(gè)狀語從句，完整的句子是: once if it is designed.
