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.
D. They had larger beaks.
Due to the drought they would need to dig deeper for food. But their tiny beaks could not do that. So over time their beaks grew and adapted to the drought. Therefor the answer is D. They had larger beaks!
Hope this helped! <3
<span>He was the first person to figure out genetics well enough to be able to predict the results of crosses that he made.</span>
1. Notify teacher
2. run the cut under warm water with soap to clean the wound
3. secure the wound with a bandage
4. make sure the glassware is properly disposed (by teacher)