如图,AB是半圆O的直径,AC为弦,OD⊥AC于D,过点O作OE∥AC交半圆O于点E,过点E作EF⊥AB于F,若AC=4,则OF的长为( )
A:1
B:32
C:2
D:4
说说下列句子运用的修辞方法
哪里要开山,哪里要架桥,哪里要把陡坡铲平,哪里要把弯度改小,都要经过勘测,进行周密计算。____
It was late. She opened the door ________ because she didn't want to wake up her grandma.