_____ a reply, he decided to write again.A. Not receivingB. Receiving notC. Not having receivingD. Having not receiving 答案:C 现在分词的完成形式表示动作发生在主句动作之前。 3.下列关于碳及其化合物的说法,正确的是( )A.CO2的排放不是导致酸雨的原因B.CO和CO2都可将氧化铜还原成铜C.在室内放一盆澄清石灰水可防止CO中毒D.铅笔字迹易变模糊是因为常温下石墨化学性质活泼