Answer:19. He says that he’s been really tired since several weeks ago. 20. A friend of us is going to pick us up at the airport. 21. I’ve worked like a waiter in the past, but I wouldn’t want to do it again. 22
Explanation:
The answer is C :
It controls the entry and exit of substances.
Answer:
Aluminum, because it is in group 13 and has three valence electrons.
It has no effect. If you are not tampering with the substance and just observing, nothing will change
