If each sandwich consists of one type of bread, one type of cheese, and one type of meat, which best represents four of his possible sandwich choices?

WST, WGF,  WSC, WGT

Step-by-step explanation:

As each sandwich consists of one type of bread, one type of cheese, and one type of meat, there must be one letter out of W, I and B. There must be one cheese and there must be one letter out of G and S. There must be one meat and there must be one letter out of C, T, F and H.

The possible combinations must include three letters. Thus  WSTWG, WS, WC, WTWGT, WSHWGSC and WGSF  could not be the right choices.

The possible combinations are WST in which W is for wheat bread, S is for sliced cheese and T is for turkey meat.

WGF,  in which W is for wheat bread, G is for grated cheese and F is for fish meat.

WSC, in which W is for wheat bread, G is for grated cheese and F is for fish meat.

WGT, in which W is for wheat bread, G is for grated cheese and T is for turkey meat.