For a virus to enter a cell, it may first recognize its membranal proteins, such as glycoproteins cell uses to recognize their media, including physicochemical variables, such as temperature, pH, and solute concentration, but also other cells, and pathogenic agents, such as a virus. These structures which are proteins are also known as cell receptors (as we can see in the third answer option), and they are encrusted in the membrane of the cells. we can see this graphically in the pictures below.
Here, with the orange polygon, we can see how the virus and the cell first match together with the cell receptor.
In this picture, we can see an example of an infection by the Sars-CoV-2 entering the cell via the cell receptor, in this case, the ACE2 receptor.