Which factors are most likely to affect whether a galaxy will evolve by merging with a second galaxy? Select the two correct answers.

The two factors that are most likely to affect whether a galaxy will evolve by merging with a second galaxy are:

1. **Its size compared to that of the other galaxy**: The relative sizes (mass) of the galaxies are significant in determining the likelihood of a merger. Larger galaxies have stronger gravitational pulls and can more easily attract smaller galaxies.

2. **Its proportion of gas compared to that of the other galaxy**: The amount of gas can influence the dynamics of a merger and the subsequent star formation activity. Galaxies with higher gas content can interact differently compared to those that are more evolved and have less gas.

Distance and age are generally less critical in the context of whether a galaxy will merge, although they can play a role in the dynamics of interactions.