Explorer Robert Ballard searched the sunken ship—the Titanic for more than 20 years and also, with his cameras, he _____ the hole along the side of the ship which had caused it to fill with water and sink

_ with care, one paper-bag will last for sixweeks

下列各句中，表达得体的一句是

It takes me two hours ______ my homework every day.

do you know so much about the UFO—I usually get the information by surfing the Internet.