(1)图1为元素X的前五级电离能的数值示意图。已知X的原子序数<20，请写出X基态原子的核外电子排布式       。

(2)A、B、C、D、E、F、G、H八种短周期元素，其单质的沸点如图2所示。

请回答：

①上述元素中，某些元素的常见单质所形成的晶体为分子晶体，这些单质分子中既含有σ键又含有π键的是       (填化学式)。

②已知D、F、G三种元素的离子具有跟E相同的电子层结构，则B、C、D三种元素的第一电离能由大到小的顺序为(用相关元素符号表示)       。

③已知H的电负性为1.5，而氯元素的电负性为3.0，二者形成的化合物极易水解，且易升华。据此推测该化合物的化学键类型为       。

④原子序数比A小1的元素与D元素形成的化合物的空间构型为       ，中心原子的杂化方式为                                           。

A child is sent to the school nurse because, according to his teacher, he's constantly scratching his head. When the nurse assesses his hair and scalp, she finds evidence of lice. What did she probably see ？（）

A．Flaking of the scalp with pink, irritated skin exposed.

B．Small white spots that adhere to the hair shaft, close to the scalp.

C．Scaly, circumscribed patches on the scalp, with mild alopecia in these areas.

D．Multiple tiny pustules on the scalp with no abnormal findings on the hair shafts.