一、关于网友这道题的答案分析：

这道题中的 favourite 要变为复数名词，主要原因是 favourite 是单数可数名词，而它前面没有任何限定词（比如冠词、指示代词、物主代词等），所以要变为复数，这种情况如果不用复数，就构成语法上所谓的“光杆名词（bare noun）”（即单数可数名词单独使用，就像“光杆司令”一样），这种情况通常是不允许的（例外的情况如 by plane, all day, from door to door 等另当别论）。下面举一个简单的例子：

不可以说：He likes child.（光杆名词）

但可以说：He likes children.（用复数名词）

也可以说：He likes this child.（有限定词修饰）

也可以说：He likes your child.（有限定词修饰）

……

二、再回到such as...前面的名词是否一定要用复数——such as前面的名词可以有多种可能。

●复数名词+such as...：这是大家比较熟悉的用法。如：

Do not ignore warning signs such as tiredness. 不要忽视疲乏等健康警示。

There are plenty of distractions such as sailing. 有许多消遣方式，如航海。

There are few poets such as Keats and Shelly. 像济慈和雪莱这样的诗人现在很少了。

In some places, such as restaurants, the men’s and women’s rooms are free for their customers. 在有些地方，例如饭店，男女卫生间客人都是可以免费使用的。

Cartoon characters such as Mickey Mouse and Snoopy are still popular. 米老鼠、史努比等卡通人物仍然流行。

Children should be encouraged to take up outside interests, such as music or sport. 应该鼓励儿童去培养自己的课外爱好，比如音乐或体育。

●单数可数名词+such as...：这样用的单数可数名词通常表泛指（比如连用不定冠词）。如：

A man such as him will surely succeed. 像他这样的人一定会成功。

We wouldn’t give the ticket to a fool such as him. 我们不愿把票给像他那样的傻瓜。

Take up a relaxing hobby, such as knitting. 从事一种让人放松的业余爱好，比如编织。

●不可数名词+such as...：该用法也需引起注意。如：

Information such as this is freely accessible to the public. 像这样的信息是向公众自由开放的。

Eye operations often involve the use of highly sophisticated equipment, such as lasers. 眼部手术经常使用高度精密的设备，如激光。

They don't allow any antisocial behaviour such as continuous lateness.他们不允许出现像经常性的迟到这样有违社交礼仪的行为。

●某些代词（比如不定代词）+such as...

Don’t do anything silly such as marry him. 不要做什么蠢事，比如说去嫁给他。

A frame is an object made from long thin pieces of something such as wood. frame是一种由诸如木头之类的细长条状物制成的物体。

●两点补充：

1.这里所说的“跟在后面”，不一定是“紧跟在后面”（比如为了保持句子平衡）。如：

Foods which are known stimulants should be avoided, such as coffee and chocolate. 凡已知能引起兴奋的食品，如咖啡和巧克力，都应该避免。

2.最后提醒一句，不要将上面用法中的 such as（表示列举）与下面的such as相混淆（as是关系代词）：

He is not a man such as I admire. (=He is not such a man as I admire.) 他不是我钦佩之人。

I can't find a book such as I want. (=I can't find such a book as I want.) 我找不到想要的书。

A plan such as you propose will never succeed. (=Such a plan as you propose will never succeed.) 像你建议的这种计划永远不会成功。