Infant dependency in humans may have lead to the common pattern that we see in humans of pair-bonding.

婴儿依赖大人可能导致了我们人类的一夫一妻关系。

youdao

In the wild, a single parent can't provide both food and constant care for its young, so nature invented pair-bonding - couples.

在野外，单亲无法为自己的幼子食物和悉心呵护，所以自然界发明了一雌一雄的配偶。

youdao

The nerve cells in the prefrontal cortex of the fathers also contained more receptors for vasopressin, a small peptide that influences social behaviour and pair-bonding.

父绒猴前额叶皮层的神经细胞也包含更多的后叶加压素受体（receptors for vasopressin），是一种较小的/短肽（peptide）分子，对社交行为和配偶间关系有影响。

youdao

So if we take a look at nitrogen here, what you'll notice is we have thre available for bonding, - and we already have our lone pair -- one of our orbitals is already filled up.

如果我们看一下氮原子，我们注意到我们可以成3个键，我们已经有一个孤对-,其中的一个轨道已经被填满了。

麻省理工公开课 - 化学原理课程节选