A reliable but invalid test is one where the measurements are consistent but not accurate or true to the actual value being measured.
The best statement that describes this scenario is:
A. You measure the temperature of a room with two thermometers and they both say the room is below 0°C, but you know the room isn't cold.
In this case, the thermometers are providing reliable (consistent) results that are invalid (not true to the actual temperature of the room).