例：Those ____ (test) positive are quarantined to stop the spread of Covid-19. 检测为阳性的人要被隔离以阻止新冠的传播。
答案是testing，为什么不用tested表示“被检测”？
test既可做及物动词，也可做不及物动词，因此就语法而言，本题用testing（主动含义）和tested（被动含义）都是正确的，不过实际上，除非特别强调“被动”，通常表达“某人检测为阴性/阳性”是用testing，如：
1. She tested positive for AIDS.（韦氏词典）
2. By measuring what happened to people within 14 days of testing positive, researchers found that people infected with delta were more likely to seek medical care at a hospital or emergency room compared to people infected with the alpha variant.
