Select the thesis statements that are most unified.

Teen magazines are an inexpensive source of well-written fiction and nonfiction.
Teen magazines are an inexpensive source of well-written fiction.
Teen magazines are an inexpensive source of well-written nonfiction.
Teen magazines are an inexpensive source of reading materials.

Teen magazines are an inexpensive source of well-written fiction and nonfiction.

Teen magazines are an inexpensive source of reading materials.

The most unified thesis statement is "Teen magazines are an inexpensive source of well-written fiction and nonfiction."

To determine which thesis statements are most unified, we need to consider whether the statements share a common theme or focus. In this case, the common theme is that teen magazines are an inexpensive source of reading materials.

Let's analyze each thesis statement:

1. "Teen magazines are an inexpensive source of well-written fiction and nonfiction."
This statement includes both fiction and nonfiction, which are both types of reading materials, so it is unified.

2. "Teen magazines are an inexpensive source of well-written fiction."
This statement focuses only on well-written fiction, which is a type of reading material, so it is also unified.

3. "Teen magazines are an inexpensive source of well-written nonfiction."
This statement focuses only on well-written nonfiction, which is again a type of reading material, so it is also unified.

4. "Teen magazines are an inexpensive source of reading materials."
This statement generalizes that teen magazines provide reading materials, without specifying whether it is fiction or nonfiction. Although it is a valid thesis statement, it is not as specific or unified as the previous statements.

Based on the analysis, the most unified thesis statements are:
- "Teen magazines are an inexpensive source of well-written fiction and nonfiction."
- "Teen magazines are an inexpensive source of well-written fiction."
- "Teen magazines are an inexpensive source of well-written nonfiction."