What am I am a _________________________________________.请回答!

What am I am a _________________________________________.请回答!
A、My first is MAT ,but not in CAT.
B、My second is in TOP,but not in TIP.
C、My third is in NEW,but not in DEW.
D、My fourth is in SKY,but not in SHY.
E、My fifth is in TOM,but not in TOY.
F、My sixth is in BUY,but not not in BUT.