Need help it is a test What does the author suggest by using the word wealth in the paragraph below?

But the stone structure isn't the only thing that has lasted over the years: the Colosseum is also home to a wealth of plant species. In fact, a study in 1855 revealed as many as 420 plant species growing in and around the stone structure.

A.
The plants have been sold.
B.
There are a large number of plants.
C.
The plants are expensive.
D.
The plants are quite rare.