Which quantity is equivalent to 50 kilocalories

I believe this problem have these following choices:

5,000 cal

0.05 cal

5 x 10^3 cal

5 x 10 ^4 cal

Now 1 kilocalorie  = 1000 calories, therefore:

50 kilocalories * (1000 calories / 1 kilocalorie) = 50,000 calories

Since there are 4 zeroes, so the scientific notation is:

5 x 10 ^4 cal         (ANSWER)

it means there are 3 atoms of oxygen