The increase in the use of online dating websites can best be explained by
a. better available technology that makes the websites more personal
b. an increase in available services that appeal to older persons looking for dates
c. the fact that divorced persons fear they will end up alone in old age
d. the fact that dating sites are likely more efficient than meeting in person

D

Explanation:

The fact that dating sites are likely more efficient than meeting in person and would be the first step of knowing people.

The increase in the use of online dating websites can best be explained by the fact that dating sites are likely more efficient than meeting in person .

d. The fact that dating sites are likely more efficient than meeting in person

Explanation:

Online dating websites offer the convenience of not having to meet in person in order to know each other better.

A long as the users are not sure about the credibility and genuineness of the person on the other end, they can choose not to share any personal information about themselves.

Moreover, these websites also provide facilities like video calling and picture sharing which cease the need to meet up physically.

i would say b. research typically uses a variety of sources