Vật A=20Hz

Vat B= 10Hz

Vì van goc truyen am trong chat ran nhanh hon van tóc truyen am trong chat khí khi ngựa chay den thi am truyen qua dat den tai nguoi nhanh hon khi am truyen trong ko khi den tai nguoi nen khi áp tai xương dat thi ta co the nghe thay tieng vo ngừa chay

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

He is coming _______a cold after a night out in the rain.

A. down with

B. across with

C. up with

D. away from