Krypton is a noble gas and because it has its valence electrons filled, it is very hard for it to react with things.
It is not a halogen as they are extremely reactive.
I believe C.) would be the best answer
C) It makes the overall crop more susceptible to pests or disease. is the correct answer
A virus's ability to infect an animal cell depends primarily upon the "<span>presence of receptor sites on the cell membrane"
Hope this helps!</span>