Fact 1: Rivers are usually larger than streams.

Fact 2: Second half becomes rocky with small stream crossings some standing water.

Given the two facts above, answer the question "what are usually larger than small water crossings?" with the following options: 
- alveoli
 - an anion
 - tortoises
 - tail fins
 - engines
 - rivers
 - Inches
 - vehicles


 

      rivers   