Answer:
If we stopped shaking hands there may be, for an older generation, a sign of a lack of respect (though that can be shown in other ways).
Explanation:
Shaking hands is used as a form of greeting, expressing gratitude, and even used to complete business or diplomatic agreements. So, it does play an important role is society, but at the same time, I do believe that there are other ways of showing respect, a greeting, or completing agreements.
"Swimming laps is a good exercise." Is gerund
D, notice how the first 3 answers are alike! They are all personal where as the 4th is more of a statement not made personally