The missing boys were last seen ________ near the river.
A
所填的词为主语补足语，因其后有明确的地点，补足语表示动作当时正在进行中，所以只能使用playing。
The house was quiet in the night, ________ the occasional coughing from my throat.
Touristexpenditureshavedifferenteffectsonadestinationeconomy:salesbyfoodvendorstorestaurantsare_______effect;whiletaxifaresandairlineticketsalesare_______effect.
The Western Council for Travel Research in _______ employed the term visitor.
Heshookhandswiththevisitors________astoconveyhisapology.