Alist of 300 numbers start at 1.after that every number is tripled the number which it had precedes it. the 200th number on the list is
a: 600
b: 900
c: 3 to the 199 power
d: 3 to the 200 power

Since each term is a multiple of the previous term, this is a geometric sequence, because there is a common ratio.  (The constant found when dividing any term by the previous term.)  Any geometric sequence can be expressed as:

a(n)=ar^(n-1), where a=initial term, r=common ratio, n=term number:

We are told that a=1 and r=3 so

a(n)=3^(n-1), so the 200th term is:

a(200)=3^199

So your answer is C.