1. 必要产品：necessary operation ==> 必要的动作,必要动作 | necessary product ==> 必要产品 | necessary protection ratio ==> 必要保护率
1. So it is necessary to ask the salesperson questions and make clear what you want to avoid buying the same product more than once.
2. The Chinese government had approved of US companies issuing product recalls, and it would thoroughly investigate problematic Chinese firms and penalize them when necessary.
3. In order to buy a branded product, some of them would cut down on food and clothing and other necessary expenses.
4. It's a necessary product for any open market, which China has shown to be moving toward.