Express this is scientific notation 0.003045 a) 0.3045 x 10-2 b) 3.045 x 103 c) 3.045 x 10-3 d) 30.45 x 102 `

Place the decimal point right after the first nonzero digit, which is 3. 

So you'll go from this  to this  after this move.
 
Now ask yourself: "how many spots must I move the decimal point to get back to 0.003045?"

The answer is "3 spots to the left"

The exponent of the final answer is -3
The negative indicates "move left" and the 3 tells us how many places to move the decimal

Therefore, 

Choice C)
This is assuming you meant to write the -3 as an exponent

Welp life just is hard