题目
(2009辽宁卷理)正六棱锥P-ABCDEF中,G为PB的中点,则三棱锥D-GAC与三棱锥P-GAC体积之比为(A)1:1 (B) 1:2 (C) 2:1 (D) 3:2 答案:C解析:由于G是PB的中点,故P-GAC的体积等于B-GAC的体积 在底面正六边形ABCDER中 BH=ABtan30°=AB 而BD=AB 故DH=2BH 于是VD-GAC=2VB-GAC=2VP-GACThey felt so _____ that they _____ go to bed early.
[ ]A. excited; couldB. excitedly; couldC. excited; couldn'tD. excitedly; couldn't