China had invaded Vietnam
Answer:
Explanation:
Enzymes act as biological catalysts (a catalyst is a chemical that speeds up chemical reactions within the cell.) Enzymes are able to speed up the rate in which chemical reactions occur by reducing the activation energy (energy needed to start a chemical reaction)
Answer:
The wall was built to help keep out northern invaders like the Mongols. Smaller walls had been built over the years, but the first Emperor of China, Qin Shi Huang, decided that he wanted a single giant wall to protect his northern borders.
