2．The ‘April Fools’ tradition is said_________ in the sixteenth century.

A．to start

B．to be starting

C．to have started

D．to have been starting

高血压脑病是血压突然升高，造成脑血流自动调节机制的障碍，此时平均动脉压应高于（）。

A.160mmHg

B.170mmHg

C.180mmHg

D.190mmHg

E.200mmHg