"Flap" sounds like something (a flag, a sail) flapping, and "flop" is the dull sound of something falling down flat.

而flop听着就象什么东西直直落地发出的沉闷一响.

youdao

"Flap" sounds like something (a flag, a sail) flapping, and "flop" is the dull sound of something falling down flat.

而flop听着就象什么东西直直落地发出的沉闷一响.

youdao