Hey，Kate，I called you at 6：30 yesterday evening，but you didn't answer．
Oh，sorry．I ______ at that time．（ ）
A．am doing the dishesB．do the dishes
C．was doing the dishes
Around the world， 300 million tons of plastic ________ each year， of which about 10 percent ends up in the sea． （ ）
A．is createdB．was created
C．creates
"Left﹣ behind" children _______ see their parents， because their parents work in the cities leaving them behind in the countryside to be cared for by their grandparents． （ ）
A．alwaysB．hardly ever
C．often
Ants are pretty small． You might think that they _______ be rather weak． But what you might not know is that ants are actually very strong for their size． （ ）
A．needB．can'tC．must
Tennis can exercise all of our muscles （肌肉）． And it requires ________ to spend time with others． This is good for our health too． （ ）
A．oursB．usC．we
A recent survey shows that 44 percent of Americans want to use self﹣driving cars，_______ 34 percent believe that they will make the roads more dangerous． （ ）
A．althoughB．becauseC．if