人体胃液中含有少量盐酸，下列图象能正确反应人喝水时，胃液中盐酸溶质质量分数变化情况的是[ ]
A.
B.
C.
D.
答案：B
Tom couldn’t ___ those forms until I had explained how to do it twice.
A．go through
B．come up
C．deal with
D．look for
RNA的结构有何特点？它们怎样发挥生理功能？
