Step 1: Understanding the import statement.
In Python, the \texttt{import} statement allows us to bring in libraries or modules into our script. When importing, you can assign a shorthand name (alias) to the module using \texttt{as}. This helps in reducing the need to reference the entire module name repeatedly.
Step 2: Evaluate each option.
- Option (A) Key: In Python, a key usually refers to the key in a dictionary. This is not applicable here.
- Option (B) Alias: The \texttt{plt} in this case is the alias for the \texttt{matplotlib.pyplot} module, making this the correct answer.
- Option (C) Variable: A variable holds a value or object, which is not the case here.
- Option (D) Function: A function in Python is defined using the \texttt{def} keyword, which is not the case for \texttt{plt}.
Step 3: Conclusion.
The \texttt{plt} in the statement is an alias for the \texttt{matplotlib.pyplot} module.
Final Answer:
\[
\boxed{\text{plt is an alias for the matplotlib.pyplot module.}}
\]