Hint: We have to use the correct adjective. It is the adjective of possession. Take note that uncle David is a male and a singular noun. Use the adjective of possession accordingly.
Complete solution:
The correct answer is option b because the word his satisfies both the conditions of uncle David being a male and a singular noun.
Option a is wrong because the word they indicate that there is more than one person when Uncle David is referring to just one person. Also, the usage of are after they make no sense and is grammatically wrong.
Options c is wrong because the word there means we are indicating to someplace. For example, Keep the coffee there. So basically, there implies a location.
Option d is also wrong even though it is another spelling of the word there as used in option c. This also implies that there is more than one person and is used to show possession. for example, the students in the class did not do their homework.
Hence the correct answer is option ‘b’.
Note: One way of answering this question is to check how many people are being referred to. Also, check the gender of the person. As soon as these two criteria are ascertained, it is unlikely that you will get the answer wrong.