在英语四级学习的道路上，改错练习是提升语言准确性不可或缺的一环。通过仔细审查并修正句子中的错误，我们不仅能加深对英语语法的理解，还能提高写作和表达的准确性。下面，让我们一起进入今天的英语四级改错练习。

原文

These days, many people choose to purchase items online. It's convenience and efficiency are major factors that attract consumers. However, shopping online has its own disadvantages.

如今，许多人选择在网上购买商品。它的便捷和高效是吸引消费者的主要因素。然而，网上购物也有其自身的缺点。

Firstly, you can't try on clothes or shoes before buying, so there's a risk that they won't fit. Secondly, the quality of some products are questionable. You never know if they're genuine or fake until you receive them.

首先，购买前无法试穿衣服或鞋子，因此存在不合身的风险。其次，有些产品的质量值得怀疑。在收到货之前，你永远不知道它们是真的还是假的。

Additionally, online shopping can be addictive. People tend to overspend and buy unnecessary things that they don't actually need. Therefore, while online shopping has its benefits, we should be cautious and make wise decisions when purchasing items online.

此外，网上购物会让人上瘾。人们往往会超支，买一些实际上并不需要的不必要的东西。因此，虽然网上购物有其好处，但我们在网上购买物品时还是应该谨慎，做出明智的决定。

答案解析

1.错误：It's convenience and efficiency are major factors that attract consumers.

更正：Its convenience and efficiency are major factors that attract consumers.

解析：这里需要指代“在线购物”的便利性和效率性，所以应该使用所有格形式“its”而不是主格形式“it's”。

2.错误：you can't try on clothes or shoes before buying

更正：you can't try on clothes or shoes before buying them

解析：为了使句子结构更加完整和清晰，应该添加宾语“them”来指代前面提到的“clothes or shoes”。

3.错误：the quality of some products are questionable

更正：the quality of some products is questionable

解析：主语“the quality of some products”是单数，所以动词“are”应该改为“is”。

4.错误：You never know if they're genuine or fake until you receive them

更正：You never know if they're genuine or fake until you've received them

解析：在描述“直到你收到它们”这个条件时，应该使用现在完成时“you've received them”来表示已经完成的动作对现在的影响。

5.错误：Therefore, while online shopping has its benefits

更正：However, while online shopping has its benefits (或改为Although/Despite the fact that online shopping has its benefits)

解析：虽然“therefore”在这里不是语法错误，但从逻辑上讲，使用“however”或“although/despite”更能体现出前后文之间的转折关系。

以上就是英语四级改错示例，在英语四级备考中，需要保持持续的学习和练习，不断提高自己的英语能力。