What might be the biological function of laughter?

Read this sentence from the story of my life by helen keller. the most important day i remember in all my life is the one on which my teacher, anne mansfield sullivan, came to me. which element of plot does this sentence best represent?

Read the passage from sugar changed the world. sugar is a taste we all want, a taste we all crave. people throughout the planet everywhere have been willing to do anything, anything at all, to get that touch of sweetness. we even know exactly how thrilling it was to taste sugar for the first time. when the lewis and clark expedition met up with the shoshone, who had little previous contact with old world products, sacagawea gave a tiny piece of sugar to a chief. he loved it, saying it was "the best thing he had ever tasted." sugar created a hunger, a need, which swept from one corner of the world to another, bringing the most terrible misery and destruction, but then, too, the most inspiring ideas of liberty. sugar changed the world. we begin that story with a man who could never know enough. how does the conclusion of the prologue support the authors’ purpose? select two options. it introduces the topic that will be addressed next. it provides information about the authors. it states why the topic is relevant to readers. it cites sources the authors used in the text. it explains how the authors came to study the subject.

Read the excerpt from the common sense of bicycling: bicycling for ladies. the bicycle is capable of such high speed that there is a strong temptation to ride so fast as to cause over exertion or excessive perspiration. on the other hand some people ride too slow, causing a zigzag and uncertain movement. while exercising reasonable caution, be a fearless rider. when you come to a steep hill, if the road is clear, let it go as fast as it will. if you rid yourself of that ghost of fear, coasting is one of the greatest delights of cycling. which is the best paraphrase of the text?