Cotton is one of the most important cash crops supplying raw material to an extensive textile industry. It is a widely grown crop in areas of warm subtropical climate, typically on the equatorial side of the mid-latitudes. Among the cotton producing countries the first rank goes to China. The major areas of production in China lie in the floodplains of the major rivers in the northeastern part of the country.
Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
EXAMIANS