流行性脑脊髓膜炎流行病学的主要特点是（）。

A.常呈地方性流行

B.人是惟一传染源

C.新生儿也易患流行性脑脊髓膜炎

D.流行性脑脊髓膜炎流行时，仅少数病人发展成典型的化脓性脑膜炎

E.细菌容易变异

An analyst does research about profit and loss about stock and stock option transaction. An investor simultaneously purchases a stock priced at $78 and writes a call option on that stock with an exercise price of $80 selling at $6. If the price of the underlying is $85 at expiration of the option, the profit for that investor's position is closest to（）

A. $3

B. $8

C. $11