It basically translates to "Be at your best behavior!" or "Be ready at attention" depending on the scenario.
A. Radio announcers should be careful not to insert their opinions into the newscasts.
Aaaaaaaaaaaaaaaaaaaaaaaaaa
I think the answer is C.have because if it has some than it would sound like <span>Some caterpillars _____have_____ been known to sleep during the day.</span>
