Answer:
![B. (-\infty,1]](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6zncj7mklp11espnfjggkhs17fujabjzjp.png)
Explanation:
The given function is

A function is said to be decreasing over an interval, if it has a negative slope on that interval.
We can see from the graph that, the function has a negative slope on the interval;
![(-\infty,1]](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3z0srlvzyzb7hfch4uflqjjtycdxm4u9pg.png)
But the graph has a positive slope on the interval;

The correct answer is B