The blade is the flattened portion of the leaf. These expanded blades are called lamina which are attached to the plant stem by the petiole. They come in diverse shapes, sizes, and other characteristics. The other choices are just supporting structures of this structure of the plant.
A = enzyme
B = active site
C = product
D = substrate
The correct answer is A and C.
China's geographic location, with Gobi in the North, and to the West is Himalaya and seas to the east and south, which isolated early chinese civilization from other cultures.
C. China's civilization which is the oldest continuous civilization which i found in the world.
China civilization is the oldest written record in history. In the writings of shang they don't indicate any existence of the Xia.
For letter a, it is not advised to cut towards yourself. Although you might not harm the people surrounding you, you can't afford to risk yourself. For letter b, do not apply so much force. Just apply the minimal force, just strong enough to cut through. For letter c, you have to wear the goggles all the time for safety purposes. For letter d, I think this is the answer. When you only want to cut the skin, it would be better to use scissors.