Use reasoning to lead to the answer of the following question:
Where on a river can a human hold a cup upright to catch water on a sunny, clear day?\nOptions:\n- bridge\n- waterfall\n- mountainous area\n- planet earth\n- valley

waterfall
There cant be rainfall on a sunny clear day.

From a waterfall, water can be catched in a cup hold upright.

Waterfall can take place on a sunny clear day.

.

So, the answer is waterfall