They housed eight adult rats with two types of robotic rat—one social and one asocial—for four days.

他们将8只成年老鼠和2种机器老鼠（一种是社会性的，一种是非社会性的）一起饲养了4天。

youdao

A previous Pew Research Center analysis projected that as many as one-in-four of today's young adult may never marry.

皮尤研究中心此前的一项分析预测，当今年轻人中可能有多达四分之一的人这辈子都不会结婚。

youdao

Since last year, four more states reported adult obesity rates of more than 30 percent - meaning that at least 30 percent of their populations are obese.

VOA: standard.2010.07.02

Less than one in 10 NHS paediatric consultants has identified time for research, in contrast to one in four adult physicians.

BBC: Children 'missing out on research benefits'

The 59-year-old mother of four adult children says her Mexican parents and grandparents taught her a respect for the law at an early age.

CNN: STORY HIGHLIGHTS

Murdoch uses the occasion to make a request of his four adult children: that they agree to alter the terms of the family trust to give his two young daughters from his third marriage voting rights.

FORBES: That Rupert Murdoch Script No One Will Touch? We Have It.