下列有关时区的说法，正确的是（  ）

在△ABC中，若| $\overrightarrow{AB}$ + $\overrightarrow{AC}$ |=| $\overrightarrow{AB}$ ﹣ $\overrightarrow{AC}$ |，AB=2，AC=1，E，F为BC边的三等分点，则 $\overrightarrow{AE}$ • $\overrightarrow{AF}$ =（  ）

    We can't live without love and we know what love is, but we don't say only humans know what love is. Yes, it's impossible for animals to do some things because of their physical body. However, sometimes some of them might be able to show us the love that we have forgotten on our "busy road", just like the following story.
    A dog, was knocked down by a car and died in the middle of the road. Later, another dog ran beside the body of the dead dog and he tried to wake his friend up using his legs. When his effort to wake up his friend failed, he tried to push his friend to the roadside. But his friend was too heavy for him to push.
    Though traffic was busy and dangerous, he wouldn't want to go away from his friend, just standing beside his friend shouting and crying.
    A lot of people saw this story and were very touched (感动的). Even a dog can show his loyalty (忠诚) and love to his friend, what can our humans do?

①加强宪法监督需要完备的制度措施　    ②加强宪法监督只是对国家公职人员提出的要求

③加强宪法监督需要人们增强宪法意识　④国家可以通过各种途径，开展各种活动，增强人们的宪法意识

美国国家科学基金会2010年9月29日宣布，天文学家发现一颗迄今为止与地球最类似的太阳系外行星如图所示，这颗行星距离地球约20亿光年(189.21万亿公里)，公转周期约为37年，这颗名叫Gliese581g的行星位于天枰座星群，它的半径大约是地球的1.9倍，重力加速度与地球相近.则下列说法正确的是

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