The first one because just think about how light oxygen or air is
We can only see a small part of the electromagnetic spectrum
Answer:
Feeling sick. People with advanced cancer often have problems with feeling sick (nausea) or being sick (vomiting). These can be caused by treatment with chemotherapy or radiation therapy, cancer growth, blockage of the bowel or the location of the cancer.
Explanation:
The answer is 100%. Three are observable, but the fourth is just a carrier.