题目

Marmoset monkeys exist on a branch of the evolutionary tree that is distinct from the one that led to mans. But they constantly astonish researchers with ________ behavior that seems pretty highly evolved. Their social organization and ________ practices could have been the model for the phrase “It takes a village.” A dominant male and female breed, and their babies are carefully looked after by extended family members who then aren't free to breed themselves.A new study further ________ the marmoset’s reputation for admirable community values. Researchers report that these caregivers sh在场强为E，方向竖直向下的匀强电场中，有两个质量均为m的带电小球，电量分别为+2q和-q，两小球用长为L的绝缘细线相连，另用绝缘细线系住带正电的小球悬于O点而处于平衡状态．如图所示，重力加速度为g，细线对悬点O的作用力等于______．