Answer: E. By means of
Explanation:
The correct answer is "By means of" because it indicates the method or tool used to simulate communities containing various plants and animals. Here, ecologists are using computers as a means to simulate the communities.
Reasons for eliminating other options:
A. "According to" does not fit the context as it does not indicate the method or tool used for simulation.
B. "For" does not provide any information about the method or tool used for simulation.
C. "Seeing that" does not indicate the method or tool used for simulation.
D. "Since" does not indicate the method or tool used for simulation.
Therefore, the most appropriate answer is "By means of" as it clearly indicates the use of computers as a tool for simulation in this context.

Explanation:

The correct answer is option 'E' which states "By means of". Let's understand why this option is the correct answer by analyzing the given sentence and the meaning of each option.

The sentence states that "ecologists have simulated communities containing various plants and animals." This means that ecologists have created computer models to simulate or imitate real-life communities that consist of different plants and animals. The purpose of these simulations is to study and analyze the interactions and relationships between the different species in these communities.

Let's analyze each option and understand why they are incorrect:

a) According to - This phrase is used to introduce or give a reference to a source or authority. However, in the given sentence, there is no reference being made, but rather an action being described (simulating communities).

b) For - This preposition is used to indicate a purpose or reason. However, in the given sentence, there is no purpose or reason being stated, but rather a method or means being described (simulation using computers).

c) Seeing that - This phrase is used to introduce a reason or explanation. However, in the given sentence, there is no reason or explanation being provided, but rather an action being described (simulating communities).

d) Since - This conjunction is used to introduce a reason or cause. However, in the given sentence, there is no reason or cause being stated, but rather an action being described (simulating communities).

Correct answer:
e) By means of - This phrase is used to indicate a method or way of doing something. In the given sentence, it accurately describes how the communities were simulated - using computers. Therefore, "By means of" is the correct answer as it accurately reflects the method used to simulate the communities.