Concept:Match the actual consonant sound of the underlined letters, not their spelling.
Explanation:The underlined letters in the stem produce the consonant sound /n/.
This happens in words like "knee" or "gnaw", where one of the underlined letters is silent.
In "knock", the "k" is silent, so the word begins with the same sound /n/.
"Hymn" ends with /m/, not /n/, because the "n" is silent.
"Pink" and "sing" contain the sound /ŋ/, which is different from /n/.
Only "knock" shares the same consonant sound as the stem.
Answer:A. knock