New research（研究) about how much time people spend on their smartphones(智能手机) per day.

小题1:People cannot use the smartphones to _________________

A．read e-books

B．send text messages

C．take photos

D．play football小题2:Smartphone owner spends most of the time _______________ every day.

A．surfing on the internet

B．listening to music

C．watching videos

D．making phone calls小题3:Making phone calls with the smartphone was only the _____ most popular use.

A．first

B．sixth

C．twelfth

D．fifth

抗牙本质敏感药应具备的条件是（）

A.对牙髓没有刺激性

B.能消除或减轻牙本质过敏症所引起的疼痛

C.不刺激口腔软组织

D.疗效稳定持久

E.以上均正确