Diagram 17 shows Puan Lily cooking in a kitchen.

图17显示丽丽女士正在厨房里准备食物。

Diagram 15 is an incomplete bill which shows two items bought by Puan Anita.

图15是一张不完整的单据。它显示亚妮达女士所购买的两项物品。

Puan Rika is preparing food in the school canteen. Which of the following is the most effective for preventing bacteria from spreading to the food?

丽卡女士正在学校的食堂准备食物。下面哪项能最有效地防止细菌散布到食物里？