The answer is letter A. When you notice the soft sound of rain on the roof, it has crossed a perpetual line called your absolute threshold for detecting an auditory signal. Absolute threshold is the smallest energy that stimulates our human senses such as hearing, seeing, smelling, etc.
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The exports of San Juan, Puerto Rico are chemicals, electronics, clothing, canned tuna, rum, beverages, and the last one is medical equipment.
The imports are Gasoline, other fuels, Passenger vehicles, Medical instruments, and Sulfonamides
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Waterwheel, Ḥamāh, Syria, similar to those long used for irrigation in the Tigris-Euphrates region. In Iraq most of those crops depend on irrigation, which can be applied in three ways: by flow from rivers and canals through small channels, by lifting with wheels or pumps into channels, and by direct inundation.
The Olmecs<span> were the first major civilization in Guatemala and Mexico following a progressive development in Soconusco and modern southwestern pacific lowlands of Guatemala. They lived in the tropical lowlands of south-central Mexico, in the present-day states of Veracruz and Tabasco. </span><span>Olmecs believed they were descendents of jaguars</span>