具有研究期相对较短特点的是
A.RCTB.模型分析C.人群研究D.回顾性研究E.WYP
参考答案:B
Rather than go through the extreme hot weather and see the World Expo, I prefer ______ at an air-conditioned room and watch TV.
A.staying
B.to stay
C.stayed
D.had stayed
背书人、承兑人、保证人在票据上的签章不符合法规规定的,改票据无效。( )