Subject: In the number, 24.090, why isn't the first '0' a significant figure?

This question was submitted to me on a test and I think I got it 
wrong.  I don't know why.  I thought that the first "0", after the 
decimal, was a place holder, therefore, a non-significant figure.  

Actually, the question was:"How many significant figures are in the 
number, 24.090?"  The possible answers were A.)3  B.)4  C.)5  D.)none 
of the above.  I put the answer, B.)4, because I thought the first "0" 
was non-significant because it was a place holder.  

If it is no trouble, I  would like this question directed to Robert L. 
Judge, because he is my teacher at Holy Cross.  He thought it might be 
a good idea to ask him this way.

By the way, Mr. Judge, could you tell me my grade in Chemistry?  I 
would really appreciate it.  I hope by now it is an "A".

Re: In the number, 24.090, why isn't the first '0' a significant figure?