Answer:
Scientists are creating vaccinations that prevent people from getting the bird flu. If the virus mutates, a new vaccine will need to be made. The vaccine needs to be tested, which can be dangerous. It will also take a long time for scientists to know whether the vaccine works or not.
Explanation:
The flu vaccine is injected under skin in a inactive form and the immune system responds with antibodies to the food protecting you from the future exposure to the flu. That's why sometimes you get the flu even though you got a shot because there's different forms of the flu.
Answer:
The correct answer is D.
Explanation:
A is very informal due to the use of slang such as ''ain't''.
B has an informal tone and language due to the usage of 'you guys' to address other people.
C is very informal due to the use of shortened street slang ''Y'all'' commonly used in informal set-ups for example among friends.
They both mean like another word for a word
