I guess formal and informal refer to two types of essay - you can write a formal essay where you avoid conversational language and such and where you need to be very professional, or you can write informally where you don't have to think about such things, it is very casual.
Answer:
Is the students had learned about photosynthesis?
Answer:
She is nervous because the nurse is bringing her big
news about Romeo is the answer.
Its definetly declarative because they are declaring the lynx is a successful hunter
First conditional .
It’s used to describe things that we think are likely to happen in the future
