When a surfer rides an ocean wave on her surfboard, she is actually riding on. a. a crest that is toppling over. b. a trough of the wave. c. the rest position of the wave. d. a region of rarefaction.

A. a crest that is toppling over.

Explanation:

As we know that at the position of crest in a wave the velocity of motion of molecules is the least velocity or zero velocity

So as the surfer needs the stability he need a point of least velocity and maximum stability

So in that case he has to travel at the position of crest where he can obtain maximum stability and then his speed will be same as the speed of wave propagation in the direction of wave

so here correct answer would be

A. a crest that is toppling over.

.) the observation by semmelweis that more mothers died of childbed fever when their doctors also worked in the morgue

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