题目

Most people feel lonely sometimes, but it usually only lasts between a few minutes and a few hours.    36    In fact, it is quite normal. For some people, though, loneliness can last for years. Psychologists are studying this complex phenomenon, and have identified three different types of loneliness. The first kind of loneliness is temporary. This is the most common type. It usually disappears quickly and does not require any special attention. The second kind, situation-for example, family problem, the death of a loved one, or moving to a new place.   37   The third kind of已知＝5，则sin2α－sinαcosα的值是(　　)A．B．－C．－2D．2