3. Compound Constructions: 

Example: Neither country music nor heavy metal were a part of mainstream listening habits in the United States 20 years ago.

• The words combined by neither… nor…, each of which is singular. The plural verb “were” should be replaced by the singular verb “was”.
• Train your ear: Neither…nor… either…or…
• If the two words in the dotted blanks are singular, then the verb should be singular. Neither Bobby nor Sue likes
• If the two words in the blanks are plural, then the verb should be plural. Either Mondays or Tuesdays work for me.

Example: Poor pitching and defensive lapses are among the problems that plague last year’s championship team.

• Compound subjects “Pitching and …lapses” are plural. Therefore, the plural verb “are” is correct.
• Compound constructions like “…along with…”, “…as well as…”, …in addition to…”. The noun in the first blank is the true subject. What follows is just an intervening modifying phrase. Thus, the verb should agree with the noun in the first dotted blank such as: The teacher, along with her students, walks toward the classroom.