东汉时期黄河经常泛滥成灾,为此一位水利专家主持治理黄河,使黄河在以后的八百多年没有改道,这位水利专家是[ ]
A.张衡
B.王景
C.杜诗
D.郦道元
答案:D
长江和黄河同时流经的省级行政区是
①西藏②青海③宁夏④四川[ ]
A.①③
B.②③
C.②④
D.④③
The students are busy making preparations for the lecture because they will ______ the competition.
A.attend
B.join
C.take part in
D.attend to