I would go with B, or Ways to build immunity to diseases. Why? Well, just by using the word biology, we can use process of elimination. The prefix “bio” means life, so C and D already would be out. The suffix “ology” means the study of, so the word biology means the study of life. Because biology often has to do with diseases and finding cures to sustain human life spans, the only logical answer would be B. A would make no sense in terms of biology.
Be strong!
There are times when things go wrong,
But, you need to be strong,
Because it may be a temporary tide,
So be all out and don't hide, Because you are really strong
hope this helps chu
“When thinking” is the right answer (the definition of retrospect is “a survey or review of a past course of events or period of time”. So “when thinking “ is most likely the right answer.
Just try to make it as imaginable as possible let your readers feel and see what you are writing to them
