Answer:
Step-by-step explanation: When you see a square root sign, which looks like a division sign but flips up on the left side, you know that you're going to find out what times what equals the number under that top line.
In this case we have 16*4. The "*" symbol means "times."
16 * 4 = 64. (First you multiply 6*4 and get 24. Then you write down the four and carry the two. That means you now are now confident that the second number is 4 and you want the first number. 1*4 is 4 and then add the two you carried over, getting 6. So 16*4 is 64.
Now ask yourself "what times what is 64?" If you know your times tables, you know the answer is 8. But 8 isn't one of your choices. So now you look at the problems listed under "B' and "D."
Answer B wants you to multiply the square root of 16 times the square root of 4. Well, 4*4 is 16 so the square root of 16 is 4. And the second one, the square root of 4, is 2 because 2*2 is 4. So now you multiply 4*2 and get 8, which is the answer you wanted! So the correct answer is "B."