Answer:
C
Step-by-step explanation:
An approximation of an integral is given by: 

First, find Δx. Our a = 2 and b = 8: 

The left endpoint is modeled with:

And the right endpoint is modeled with: 

Since we are using a Left Riemann Sum, we will use the first equation. 
Our function is: 

Therefore: 

By substitution: 

Putting it all together: 

Thus, our answer is C. 
*Note: Not sure why they placed the exponent outside the cosine. Perhaps it was a typo. But C will most likely be the correct answer regardless.