Final answer:
A crack in the combustion chamber or clogged tubes in the radiator can both cause the rise in gauge pressure.
Step-by-step explanation:
The rise in gauge pressure when the cooling system is checked with a pressure tester can be caused by a crack in the combustion chamber or clogged tubes in the radiator. However, in this scenario, both statements A and B are correct.
When there is a crack in the combustion chamber, some of the combustion gases can escape into the cooling system, increasing the pressure. Similarly, if there are clogged tubes in the radiator, the coolant flow may be restricted, causing an increase in pressure.
Therefore, both A and B are possible causes for the rise in gauge pressure.