The fingerlike projections are villus.
the answer is a basalt rock.
It would be D, fertilization.
Answer:
1) Recursive definition: 
2) At the beginning of the 4th interval
Explanation:
1)
The initial population of the bacteria at time zero is

Here we are told that the reading is taken every two hours; we call this time interval "n", so

And also, after every time interval n, the number of bacteria has tripled.
This means that when n = 1,

And when n=2,

Applied recursively, we get

And substituting p0,
(1)
2)
Here we want to find at the beginning of which interval there are

bacteria.
This means that we can rewrite eq.(1) as

By simplifying,

Which means that

However, this means that the number of bacteria is 1,350,000 after 3 time intervals; therefore, at the beginning of the 4th interval.
Answer:columnar epithelium
Explanation:
Collecting ducts are readily recognized in the renal medulla, as relatively large tubules lined by cuboidal epithelium, in which the epithelial cells are relatively clear (i.e., not as eosinophilic as proximal and distal tubules) and have distinct cell borders