Home delivery or online shopping, ________ to all, makes it available for us to buy various

goods conveniently. [      ]

A. known          

B. knowing          

C. to be known       

D. having known

关于人克雅氏综合征的说法错误的是（）。

A、引起类似神经系统疾病

B、主要发生在老年人

C、家族性或零星偶发

D、正常情况下不传染