在T2WI上，亚急性后期及慢性期血肿出现低信号环，是因为（）

A、血肿周边出现正铁血红蛋白。 

B、血肿周边的巨噬细胞吞噬大量含铁血黄素。 

C、血肿周边钙化。 

D、血肿周边出现去氧血红蛋白。 

E、血肿周边出现氧合血红蛋白。

计算题.

1.At 12 noon my watch was correct. However, it then started to lose 18 minutes per hour.

Four hours ago it stopped completely and is now showing the time as 15:30.

What is the correct time now?

Answer: _____________________________________________________________

2.

What value of weight should be placed on the scales to balance?

Answer: _____________________________________________________________