This is heavily disputed, and honestly, it varies on a person-by-person basis. Some people are visual learners (so it's effective for them to use videos and pictures to help them study), some prefer being hands-on, etc...
Generally though, I'd say the most effective method that works for most people is through visceralisation. This is the process of associating concepts, words. phrases etc. with your different senses (sound, touch, images...). You can read up more on it by searching up "visceralisation for studying".
Answer:
True
The word "what" has four letters, the word "sometimes" has 9, and the word "never" has 5
It's a riddle
True, sleep problems indeed are a quite often occurence among children as well as adults - they do occur quite often but don't necessarily occur all the time for people to whom it does happen. At the same time, when someone suffers from sleep problems, this doesn't necessarily mean that he cannot sleep at all.
