Why is large size alone insufficient for the main title of a poster?

Correct answer: Value contrast and clear letterforms are also necessary for readability

The governing design concept is readability, which depends on more than letter size. A large title may still disappear when its value is close to the background or when its letterforms are crowded, irregular, or poorly spaced. Strong value contrast and clear shapes separate the title from its surroundings. Therefore option A is correct; size alone does not guarantee visibility, while the other choices make absolute or false claims.