Answer:
B.
Explanation:
P(something not happening)+P(something happening)=1 or 100%.
So if we have
P(something not happening)+40%=100%
Then the P(something not happening)=60% since 60%+40%=100%.
Yes I was using the event="something not happening" as the complement of something happening.
In fancy notation, some people might write:
![P(A)+P(A')=1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5815uhoev4wp38lxxlsex5gwxohfbg0d8s.png)
or
![P(A)+P(A^c)=1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/1dcvjue67d93fd4txjmx5uoqzxtn3uy0ei.png)