No. 7 High Senior 3 students are lucky to enjoy a ______ long winter vacation, compared with those of other schools, some of whom have to stay at school even during the Spring Festival.

A．fortunately

B．relatively

C．considerately

D．definitely

乙炔在空气中每立方米的含量如达到10ppm，相对应的百分含量是（）。

A.0.001％

B.0.0001％

C.0.00001％

D.0.01%