Statements : All windows are doors. No door is wall. Conclusions : I. No window is wall. II. No wall is door.

The correct answer is $\boxed{\text{E}}$.

The first statement is “All windows are doors.” This means that every window is a door. The second statement is “No door is wall.” This means that no door is a wall.

The first conclusion is “No window is wall.” This follows from the first statement, because if every window is a door, then no window can be a wall. The second conclusion is “No wall is door.” This follows from the second statement, because if no door is a wall, then no wall can be a door.

Therefore, both conclusions I and II follow.