«Otto, sprich bitte lauter, man … dich nicht!» a) höre b) hört c) hören

The correct answer is "a) hört". The sentence in German is "Otto, sprich bitte lauter, man hört dich nicht!" which translates to "Otto, speak louder, one cannot hear you!" In this case, "hört" is the conjugated form of the verb "hören" (to hear) that agrees with the subject "man" (one).