Awidely accepted way of thinking or behavior is

a. controversy
b. convention
c. fashion
d. trend

A widely accepted way of thinking or behaving is a convention.

It denotes set of generally accepted standards and norms and a way in which something is usually done. Example for convention is shaking hands when greeting someone. Controversial on the other hand is something causing people to have opposing ways.

a pirate walks into a bar with a steering wheel sticking out of his pants.

bartender: isn't that uncomfortable?

pirate: arrgh! it's drivin' me nuts!

the characters in string all have major secrets that they strive to avoid revealing throughout the play.