Knowledge in ways to do it
Ultrasound
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is approximately 20 kilohertz in healthy young adults.
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indian national census
From Wikipedia, the free encyclopedia. The decennial Census of India has been conducted 15 times, as of 2011. While it has been undertaken every 10 years, beginning in 1872, the first complete census was taken in 1881.
Happiness
Happiness is a sense of well-being, joy, or contentment. When people are successful, or safe, or lucky, they feel happiness. The "pursuit of happiness" is something this country is based on, and different people feel happiness for different reasons