Question

Which has the lowest magnitude ?

And what it means by having lowest magnitude ?

Answer 1

B has the lowest magnitude.

Explanation:

We are comparing frequencies -- with units of Hz, which is equivalent to the "number of cycles in a second". So lowest magnitude would mean "which has the fewest cycles in a second?"

In a second
A has 2000 cycles
B has 200 cycles
C has 0.00210^9 = 210^6 cycles
D has 20*10^6 cycles

So B has fewest.

I hope this helps,
Steve