be afraid to do 与doing区别
be afraid to do与be afraid of doing在语境和含义上有所区别：
1. be afraid to do表示不敢，胆怯去做某事，是主观上的原因不去做，意为"怕"。例如：She was afraid to step further in grass because she was afraid of being bitten by a snake（她生怕被蛇咬着，而不敢在草丛中再走一步）。
2. be afraid of doing表示担心出现doing的状况、结果。doing是客观上造成的，意为"生怕，恐怕"。例如：She was afraid to wake her husband. 她不敢去叫醒她丈夫；She was afraid of waking her husband. 她生怕吵醒她丈夫。
