若DNA分子的某个基因含240个脱氧核苷酸和80个鸟嘌呤,则该片段转录成信使RNA中,含有的尿嘧啶数为()
A.0~40个
B.1~40个
C.40个
D.80个
参考答案:A
David often forgets _____ his English book. [ ]
A. to bring
B. bring
C. brought
D. brings
雄黄中毒主要表现为
A.肝损害B.神经系统损害尤其是迷走神经C.神经系统损害及出D.循环系统及消化系统E.伸肌屈肌同时极度收缩