The rubbing alcohol sold in drug stores often is composed of 70% isopropyl alcohol and 30% water. In this solution

  a. both water and isopropyl alcohol are solvents.    
  b. neither water nor isopropyl alcohol is a solvent.    
  c. water is the solvent.    
 d. isopropyl alcohol is the solvent.
Correct? Thanks.

Hmm...

I think in this case the alcohol is the solvent because there is more of it.

Indeed.  When you have a mixture of two miscible liquids, the one that is present in the higher concentration is generally considered the solvent.

Unless your logic is: 'The thing you want is the solute, and the inert component you don't care about is the solvent'
in which case water is the solvent.

I call this one ambiguous.

But in the case of the alcohol problem listed above, it is simply not correct to call the water the solvent.  Based on the definition of what a solvent is, water could not be considered the solvent there.