1. The purpose of the line "<span>In these days we can kindle a fire without any trouble, because we can easily get a match..." is to imply the main idea of the article. The statement that we can easily kindle fire today implies that there was a time when it wasn't so easy. That is why people had to figure out a way to kindle a fire without looking for a natural source. All of this supports the article's main idea, that match was a brilliant invention, which we shouldn't take for granted.
2. This line shows the need for matches. People had troubles with finding the fire, but it got even harder because any fire can easily get extinguished. This proves there was an urgent need to find a way to kindle fire without having to resort to nature at all times. The line doesn't show how dependable nature is - on the contrary, it shows that humans had to find a way to not depend on it. It doesn't show how people got the fire, or how long it took to make matches.
3. The correct answer is thesaurus. It is not an encyclopedia or an ordinary dictionary, but a dictionary of synonyms, that is words with similar meanings. It also contains antonyms (words with opposite meanings) and words with related meanings. When we don't know what a word means, we use a dictionary or an encyclopedia (or Wikipedia, for that matter). However, when we know its meaning, but are looking for a more appropriate word, we use a thesaurus.</span>
The brain sends electrical signals to the muscles in the part of the body you want to move and those muscle tense up and move.
