${\left(\sqrt{x}-\frac{1}{2\sqrt{x}}\right)}^6$的展开式中常数项为(   )

阅读下面一首诗，完成下面题目。
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                                                                                                                               李商隐
                                                                                                      相见时难别亦难，东风无力百花残。
                                                                                                      春蚕到死丝方尽，蜡炬成灰泪始干。
                                                                                                      晓镜但愁云鬓改，夜吟应觉月光寒。
                                                                                                       蓬山此去无多路，青鸟殷勤为探看。

鸟类的生殖和发育过程，一般包括____、____筑巢、产卵、____和育雏等几个阶段．

①面对挫折，能够调整自己的消极情绪，具有一定的自制力

②这是意志薄弱的表现

③他错在迟到的次数太多，偶尔迟到一次并不影响意志品质的培养

④他的这种做法不利于形成良好的习惯