①若f(x)=,则f(x)在x=-1处连续   

②若则f(x)·g(x)在x=0处连续   

③若f(x)=则f(x)在x=1处连续   

④若f(x)·g(x)在x=x₀处连续,则f(x)和g(x)在x=x₀处连续

A.0                  B.1                   C.2                    D.3

A.连续                B.不连续             C.无法确定             D.以上都不正确

A.f(x)在点x=0处不连续,在点x=1处连续

B.f(x)在点x=0处连续,在点x=1处不连续

C.f(x)在点x=0和x=1处都连续

D.f(x)在点x=0和x=1处都不连续

A.32               B.23                  C.1                   D.0

A.1                 B.2                  C.3                   D.4

A.3                   B.-3                 C.±3                 D.不存在

A.连续点                                      B.无定义的点

C.不连续的点                               D.极限不存在的点

A.x=0                                      

B.x=(k=0,±1,±2,…)

C.x=0和x=2kπ(k=0,±1,±2,…)               

D.x=0和x=(k=0,±1,±2,…)

A.无极限               B.不连续             C.连续无极限          D.不连续有极限

A.充分不必要条件                            B.必要不充分条件

C.充要条件                                     D.既不充分也不必要条件