Why are water quality standers inportant

In order to protect the public health.

Explanation:

The goals of water quality standards are to protect public health and the environment , and to maintain a standard of water quality consistent with its designated uses. Water quality standards provide the "teeth" for water quality legislation and also the yardstick by which performance may be evaluated.

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering