The answer is several symptoms have be begin before age 12
ADHD is the most common psychological disorder for children that caused them unable to focus on a single thing.
The symtopms can be diagnosed by measuring the level of hyperactivity that they display pre-adolescence period.
Answer:
Primary source is more reliable, but writers tend to use both primary and secondary source.
<em>The Butterfly Effect</em> is one of the applied models in weather forecasting. It makes us understand that the reliability of forecasting drops considerably after 10 days.
Of course, the butterfly wings cannot cause a big storm, but in some cases, if the actual conditions can be studied it can have an effect, but is very hard to detect.
Professor Lovejoy, from McGill University, comments that "<em>the Butterfly Effect treats the weather as random and uses historical data to force the forecast and reflect a realistic climate"</em>.
