Answer:
Last option.
Explanation:
"The Strange Case of Dr. Jekyll and Mr. Hyde" by Robert Louis Stevenson is the Gothic novella, published first in 1886.
The given excerpt is taken from the first book the novella named, "Story of The Door". The book opens with the description of Mr Utterson, who is a lawyer by profession, and have features of 'rugged face'. He is very cold, hardly smiles, and is less talkative.
The chief jewel that the author is talking about is the Sunday walks that Mr. Utterson and Mr. Richard Enfield go for.
The passage tells that these weekly walks were so important to them that they would even resist the business calls to enjoy their walks without any interruptions.
So, the phrase 'chief jewel' is used to establish the importance of walks that Mr. Utterson and Mr. Enfield go for.
<u>The correct answer is last option. </u>
