—Are Mr. and Mrs. Wang living alone in the house?

—Yes, altough they have three sons, ______ of them live with their parents. [ ]

A. neihter

B. both

C. all

D. none

柴胡根横切面加95％乙醇及浓硫酸，可显黄绿色至绿色，其显色部位是（）。

A.木栓层以内至次生韧皮部之间

B.皮层

C.韧皮部

D.木质部

E.整个切面