The collection of cricketers in the world who were out for 99 runs in a test match is a set.

Explanation

As set is a well defined collection of objects. Therefore, the collection of cricketers in the world who were out for 99 runs in a
test match can be written as

`S={x : x` is out for 99 in the test matches, x is a crickter in the world.}

which is well defined.
Hence the collection of cricketers in the world who were out for 99 runs in a test match is a set.