Tìm các chất X1, X2, X3,... thích hợp và hoàn thành các phương trình phản ứng sau: 1.Fe2O3 +H2 ---> FexOy+X1 2.X2+X3--->Na2SO4+BaSO4+CO2+H2O 3.X2+X4-->Na2SO4+BaSO4+CO2+H2O 4.X5+X6--->Ag2O+KNO3+H2O 5.X7+X8-->Ca(H2PO4)2

Choose the best answer.

I think you should buy _____  pack of mineral water instead. And you can also buy _____  snacks such as potato crisps, 3 kilos of mandarins, 2 kilos of apples, 3 bunches of bananas, ______  cookies and soft candies.

Choose the best answer.

We should decorate our living room with _____ orange banner. We also need ________  ribbons, balloons, party hats and costume.

Choose the best answer.

I think that ______ cauliflower is not enough for 3 people. Let’s buy one more.