Cho hình hộp ABCD.A1B1C1D1 với M = CD1 cắt C1D. Khi đó: vecto AM

A. $\overrightarrow{\mathrm{AM}}=\frac{1}{2}\overrightarrow{\mathrm{AB}}+\frac{1}{2}\overrightarrow{\mathrm{AD}}+\frac{1}{2}\overrightarrow{{\mathrm{AA}}_1}$

B. $\overrightarrow{\mathrm{AM}}=\frac{1}{2}\overrightarrow{\mathrm{AB}}+\overrightarrow{\mathrm{AD}}+\frac{1}{2}\overrightarrow{{\mathrm{AA}}_1}$

C. $\overrightarrow{\mathrm{AM}}=\overrightarrow{\mathrm{AB}}+\overrightarrow{\mathrm{AD}}+\frac{1}{2}\overrightarrow{{\mathrm{AA}}_1}$

D. $\overrightarrow{\mathrm{AM}}=\frac{1}{2}\overrightarrow{\mathrm{AB}}+\frac{1}{2}\overrightarrow{\mathrm{AD}}+\overrightarrow{{\mathrm{AA}}_1}$