Which part of the influenza virion facilitates interaction between the virus and the to-be-infected eukaryotic host cell?

The choices are:
A.  Matrix protein
B.  Hemagglutinin
C.  An ion channel
D.  Neuraminidase

The right answer is B. Hemaglutinin

Explanation:
Haemagglutinins are triangular rods. They allow the attachment of Influenzaviruses on the target cells of the respiratory tree. In the presence of red blood cells, a haemagglutination (liquid medium) is obtained.
About the other components of Influenza virus:Neuraminidase is a mushroom-shaped spike composed of a tetramer consisting of 4 subunits of a single glycoprotein. At 37 ° C, the neuraminidase destroys the bonds (virus - cells) and thus allows the release of neoformed virions in the external environment: it is elution.
The membrane protein M and the protein subunits of the nucleocapsid are antigenic and are the basis of the classification of Influenzavirus types A, B and C. They induce the synthesis of non-protective antibodies fixing the complement.