He great basin receives little rainfall
1. of the encroaching mohave desert.
2. of the rain shadow of the appalachian mts.
3. of the grand canyon.
4. of the rain shadows of mountain ranges such as the sierra nevadas or southern rockies.
5. of the japanese current in the pacific ocean.

The Great Basin receives little rainfall because:

4. of the rain shadows of mountain ranges such as the Sierra Nevada's or Southern Rockies.

Explanation:

Great Basin desert is the only cold desert of the United States of America and has little rainfall due to the rain-shadow effect of Sierra Nevada's mountains.Rain-shadow Effect is such a effect in which air around the mountains absorb moisture from the surrounding area and results in the dryness of the area.The option 1 is not correct as the it is not the basic reason behind its little rainfall.The option 3 is not correct as it is not reason behind it.The option 5 is incorrect as Japanese current is not responsible for the little rainfall.  

It is c. naturally in the environment

Answerepicenter;