完形填空

先通读下面的短文，掌握其大意，然后在每小题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。

Few people like changing their habits, good or bad. Whether it is smoking, drinking or over-eating, they 1“enjoying”them to the end.

On every packet of cigarettes(香烟), people are warned against the2of smoking: “Warning: Cigarette Smoking Is Dangerous to Your Health”.3, millions of them start smoking or go on smoking. Why?

Facts show that families and surroundings(环境) play a very important part in 4 smokers. All those smokers come from smoking families or have smoking5 or relatives. Films and TV plays also play a part. People6their “heroes" on TV drinking alcohol(酒) or smoking cigarettes. “Heroes” seem to fear7, neither killing themselves nor killing others with alcohol and cigarettes. If they are not afraid of the harm of smoking and drinking,8should common people be afraid?

The simple warning on the cigarette packet does not influence smokers' habits. Even 9warnings, like showing pictures of smokers who have died of cancer, don't seem to work.  

Knowing and believing seem to be two10 things. If smoking is really as harmful as doctors say, it is time for smokers to think about it and try to give it up!

已知两点$A(1,0),B(1,\sqrt{3}),O$为坐标原点，点C在第二象限，且$\angle AOC={120}^{°}$，设$\overrightarrow{OC}=-2\overrightarrow{OA}+\lambda \overrightarrow{OB}(\lambda \in R)$,则$\lambda$等于 （ ）