Concept: The question tests the ability to identify the same consonant sound, focusing on the pronunciation of the letter "b".
Explanation:The underlined letter "b" in "best" is pronounced as the voiced bilabial plosive sound /b/.
When selecting the answer, we must look for a word in which the letter "b" is actually pronounced as /b/.
Let's check each option:
A. "comb" – the final "b" is silent, so it produces no /b/ sound.
B. "lamp" – this word contains no letter "b", so no /b/ sound can be identified.
C. "labour" – the "b" in the middle is clearly pronounced as /b/, giving the word /ˈleɪbə/.
D. "plumber" – the "b" is silent, so it does not have the /b/ sound.
Thus, the correct option is C. "labour".
Answer: C. labour