The underlined "t" in "preached" represents the sound /t/, as the past tense morphem is pronounced as /t/ if it follows a voiceless sound and /d/ if it follows a voiced sound. C. past → The "t" is pronounced /t/, making C the answer.

• A. question → question has the  /tʃ/ sound in the "t".

• B. castle → The "st" is pronounced /s/, as the 't' is silent. 

• D. lotion → The "t" is pronounced as /ʃ/