Which underlined word in the sentence is a singular common noun?

i rode my schwinn bike up and down hills on local trails.

a.
bike

b.
trails

c.
hills

d.
schwinn

Choose the sentence that is not logically connected in the paragraph. (1) one final effect of radio and tv on the language must must be noted. (2) there is no doubt that these great media of information have cut down considerably the time that used to be devoted to reading. (3) radio and tv may enhance the spoken word. (4) they tend to lower comprehension levels.