题目

已知(1＋x)＋(1＋x)2＋…＋(1＋x)n＝a0＋a1x＋a2x2＋…＋anxn(n∈N*)，若a0＋a1＋…＋an＝30，则n等于( ) A．5            B．3         C．4          D．7 答案：CThere are about two __________ workers in the newly built factory.A. hundredB. hundredsC. hundred ofD. hundreds of