A:4
B:±4
C:8
D:±8
(Ⅰ)求证:DP∥平面EAB;
(Ⅱ)求平面EBD与平面ABC所成锐二面角大小的余弦值.
There ______ a large number of students in our school. The number of the students _______ over three thousand.
人眼的晶状体相当于凸透镜,下列关于近视眼的成因说法中正确的是( )