多项式3x﹣1+6x²+4x3是( )次(      )项式，其中常数项是( )，按x的降幂排列是( )

Changing rescuers while carrying out artificial respiration should be done（）.

A.without losing the rhythm of respiration

B.only with the help of two other people

C.by not stopping the respiration for more than 5 minutes

D.at ten-minute intervals