Find the word which has a different sound in the part underlined

I find the word which has a different sound in the part underlined 
1 A the        B there.            C think.          D they
   
II put the word into two gtoups 
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there.      thrilling      bathroo .      Thunder.        Theater
than.       Weathe .     Earth.           Feather.          The
Mother     birthday      tooth           those.          Three
thing.        Bot .              Theme