To round 0.002391 to 2 significant figures, we need to look at the digits after the first two significant digits (which are 2 and 3 in this case).
The digit in the third decimal place is 2, which is less than 5. Therefore, we leave the second significant digit (3) as it is, and we drop all the digits after that.
So, rounding 0.002391 to 2 significant figures, we get:
0.0024