题目

How do you feel about watching other people work? Nothing is more refreshing on a warm summer day than watching someone else work. Right now, I’m sitting on my porch and watching young Beth baling（打捆）the big field on top of the hill. She’s been haying that field for over ten years. I know: I put her on the tractor when she was just twelve years old.  She picked a great day for baling. It’s not too hot, and there’s a nice breeze. On Monday, when she cut the field, it was so hot I thought the corn would start popping in the field. Didn’t stop her, though. She just st右图表示有关遗传信息传递的模拟实验。相关叙述合理的是（   ）  A．若X是mRNA，Y是多肽，则管内必须加入氨基酸B．若X是DNA的一条链，Y含有U，则管内必须加入逆转录酶C．若X是tRNA，Y是多肽，则管内必须加入脱氧核苷酸D．若X是RNA，Y是DNA，则管内必须加入DNA酶