花了好久把GWD语法做完了，发现里面有很多UNLIKE的题，由于我基础不好，对这个词的用法用很多困惑：

1、unlike的词性是连词和介词，用作连词时一般放在句首吗？

2、xdf老师说unlike词要对称？？？，但我不明白如何对称，比如下面这几个句子我就看不出来对称啊，还请高手详解，小妹万分感谢！

（1）  GWD-3-Q34:

Shoppers in sporting goods stores, unlike those in department stores, do very little impulse shopping; someone who comes in for a basketball will leave with a basketball only and not buy a pair of skis and a boomerang as well。

（2）  GWD-7-Q31:

Unlike the original National Museum of Science and Technology in Italy, where the models are encased in glass or operated only by staff members, the Virtual Leonardo Project, an online version of the museum, encourages visitors to “touch” each exhibit and thereby activate the animated functions of the piece.

（3）  GWD-9-Q17:

Unlike most other mergers in the utility industry, which have been driven by the need to save money and extend companies’ service areas, the merger of the nation’s leading gas company and leading electric company is intended to create a huge network for marketing the utilities in question as states open their utility markets to competition.