The temperature on Monday is −4°C. On Tuesday, it is 13° colder. What is the temperature on Tuesday?

A. −17°C
B. 9°C
C. −9°C
D. 17°C

The temperature on Tuesday is −4°C - 13°C = <<(-4-13=-17)>>-17°C. Answer: \boxed{-17}.

To find the temperature on Tuesday, we need to subtract 13 degrees from the temperature on Monday.

-4°C - 13°C = -17°C

Therefore, the temperature on Tuesday is -17°C.

Answer: A. −17°C