What is the value returned by this function: def func(): return "Hello"?

The function defined as def func(): return "Hello" is straightforward and succinct. When the function func() is called, it executes the return statement, which sends back the string "Hello" to the caller. The return value of a function is what the function outputs when it is executed, and in this case, that output is explicitly set as "Hello".

The other options do not align with what the function is programmed to return. For instance, "Hello World" is not returned because the string "Hello World" does not appear in the function's return statement. The option "None" is typically what a function returns if there is no return statement provided, which is not the case here since we have a clear return of "Hello". The term "Undefined" is not applicable in Python, as functions that don't explicitly return a value yield None, but again, this function does explicitly return a value.

Thus, the value returned by the function when called is indeed "Hello".