At the core of biology and other sciences lies a problem-solving approach called the scientific method. 1  Make an observation. 2  Ask a question. 3  Form a hypothesis, or testable explanation. 4  Make a prediction based on the hypothesis.  Test the prediction.
Xi. Xi is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh. Xi is not to be confused with the letter chi, which gave its form to the Latin letter X.
The 60-year-old Xi is the paramount political and military leader of China, ruling over 1.3 billion people (close to 20% of the world's population). China owns some $1.3 trillion in U.S. securities, making it the largest shareholder of U.S. debt. There are 122 billionaires in the country, up from zero one decade ago.