Smiling, shaking someone's hand, and saying "hello" are all ways of: being friendly listening being disrespectful sharing interests with someone

To be disrespectful would mean to do the exact opposite of smiling, shaking someone's hand, and saying "hello." So, this tells us our answer cannot be being disrespectful. Listening is something someone would do when in a conversation or when taking orders from someone. Judging by the actions the person is doing, it does not seem they are having a conversation or taking orders from anyone. It seems as though the person is barley introducing themselves. So, this tells us 'listening' is not the answer to this question. You usually discuss shared interest with another person when you're in a conversation. Again, it seems as though this person is not in a conversation, so 'sharing interest' cannot be the answer. This leaves us with our last and best option for the Being Friendly. The actions that the person is doing, leads to believe that the person is just being friendly.

An epidemic is a large and localized outbreak of a sickness or disease.  a pandemic is a large global outbreak of a sickness or disease. 

Keeps you from getting lung cancer from smoking