To solve this question, let us take one part at a time.
Part 1 (MHz to GHz)
We know that 1 MHz=0.01 GHz
Therefore, [tex]63.45 MHz=63.45\times 0.001 GHz=0.06345 GHz[/tex]
Thus, for the time being we know that Option A is correct.
Part 2 (MHz to KHz)
We know that 1 MHz=1000 KHz
Therefore, [tex]63.45 MHz=63.45\times 1000 KHz=63450 KHz[/tex]
Thus, Option B too is correct.
Therefore, Both A and B are correct. Thus, out of the given options, Option C is correct.