選詞填空；aboard/abroad/board/broad
①The ship is leaving in half an hour，so we'd better go

aboard

aboard

now.
②Although living

abroad

abroad

for years，many Chinese still observe traditional Chinese customs.
③We are asked to

board

board

half an hour before departure.
④In our village，there is a

broad

broad

（n）road，both sides of which are lined with trees.