Answer:
Cannon barrels (the automatic weapon)
Leonardo was seriously concerned by the insufficiencies of contemporary warfare, especially irritated by the time between cannon fire shots, caused by the need for relocation. Leonardo devised a multi-barreled cannon to spin a line of cannons and recharge another: a precursor of the day modern machine gun.
China opened up to the Europeans for goods, for trade and allowed missionaries to come in and to seek converts.
Answer:
d) social clock.
Explanation:
<em>The social clock </em><em>is defined as a concept or phenomena that tend to explore or figure-out different timetable that is being determined via social structure or culture that is responsible for describing a proper time related to a few specific events, for example, social status, graduation, marriage, and employment, etc. The concept of the social clock was first introduced by a psychologist named Bernice Neugarten during 1965.</em>
<em>Example: </em><em>In a few cultures, people get married very soon or early in their age whereas in other cultures people marry whenever they think they should marry.</em>
<em> </em>
The answer is: "independent [variable]" .
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