Rainforest frogs have different patterns because of incomplete dominance. Speckled frogs and polka dotted frogs blend to form striped frogs. What would be an appropriate key?

SS = speckled frogs; Ss = polka dotted frogs; ss = striped frogs

SS = speckled frogs; TT = striped frogs; ST = polka dotted frogs

SS = speckled frogs; ss = polka dotted frogs; Ss = striped frogs

TT = speckled frogs; Tt = striped frogs; tt = striped frogs