Concordance = presence of the same trait.
Identical twins have a higher rate than fraternal because most of their DNA is identical, it’s identical because the zygote split into two so the babies shared an amniotic sack. (Zygote is fertilized egg) so the baby got duplicated meaning only one egg and sperm created two babies. Fraternal twins happen when two eggs are fertilized and grow in separate amniotic sacks. So two different babies, two different eggs and sperm.
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.
The correct answer is <span>C. You cannot view live specimens because the necessary preparation kills cells. </span>
The answer is pretty self-explanatory. Unlike it, regular microscopes can view living creatures such as bacteria or similar.
Models are used to stimulate reality and make predictions