Which word can be a prefix meaning "after" and also a verb meaning "to station as a sentry"?

After his defeat in the English Civil War, Charles I was beheaded in 1649 outside the Banqueting House of which London… Who, after observing a comet in 1682, showed that it was the same one seen in 1607, 1531 and 1456? Which satirist, author of "A Modest Proposal", died in Dublin on October 19, 1745? After oil was found there in 1932, which island nation became the Persian Gulf's first oil-rich state? Which Beth Henley play about three sisters in Mississippi won the 1981 Pulitzer Prize for Drama? In September 1813, Oliver Hazard Perry "met the enemy" and won a famous naval battle on which Great Lake? After Pope Pius XI died in February 1939, Eugenio Pacelli was elected and took which name? In 2000, which Florida official certified George W. Bush as the winner of the state's 25 electoral votes?