传播途径是指病原体离开_1到达_2所经过的途径。病原体传播的主要途径有：空气传播，_3传播，_4传播。

题干

传播途径是指病原体离开____ 到达____ 所经过的途径。病原体传播的主要途径有：空气传播，____ 传播，____ 传播。

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传染源,健康人,水饮食,接触生物媒介

阅读下面材料，从每题所给的A、B、C、D四个选项中选出最佳选项

If you like peanut butter, you'll love this recipe. The steps are easy, and there's nothing to cook. You can make it all by yourself!

What you need :

2 cups graham cracker(全麦粉) 1/2 cup peanut butter

2 tablespoons sugar l/3 cup com syrup(糖水)

1/2 teaspoon cinnamon(肉桂皮) 1 cup powdered sugar

2/5 teaspoon nutmeg(豆蔻)

What you do :

First, mix together the graham cracker, sugar, cinnamon, and nutmeg in a bowl.

Next, add the peanut butter and corn syrup. Mix well.

Then, roll the mixture into balls. Place them on a large plate covered with wax paper. Leave the plate in the fridge for an hour.

Finally, take peanut butter balls out of fridge. Put powdered sugar in a small bowl. Roll each ball in the powdered sugar until it is covered.