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The hole walls for boards with two or more layers can be made conductive and then electroplated with copper to form plated-through holes.  These holes electrically connect the conducting layers of the PCB. For multi-layer boards, those with three layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. The de-smear process ensures that a good connection is made to the copper layers when the hole is plated through. On high reliability boards a process called etch-back is performed chemically with a potassium permanganate based etchant or plasma. The etch-back removes resin and the glass fibers so that the copper layers extend into the hole and as the hole is plated become integral with the deposited copper.
What type of boards undergo the etch-back process?
A: high reliability

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The battle of Iwo Jima ("Operation Detachment") in February 1945 was one of the bloodiest battles fought by the Americans in the Pacific War. Iwo Jima was an 8 sq mile (21 km2) island situated halfway between Tokyo and the Mariana Islands. Holland Smith, the commander of the invasion force, aimed to capture the island, and utilize its three airfields as bases to carry out air attacks against the Home Islands. Lt. General Tadamichi Kuribayashi, the commander of the island's defense, knew that he could not win the battle, but he hoped to make the Americans suffer far more than they could endure.
What was "Operation Detachment"?
A: battle of Iwo Jima

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The earliest recorded history of the region dates back to about 500 BCE when much, if not all, of modern Tajikistan was part of the Achaemenid Empire. Some authors have also suggested that in the 7th and 6th century BCE parts of modern Tajikistan, including territories in the Zeravshan valley, formed part of Kambojas before it became part of the Achaemenid Empire. After the region's conquest by Alexander the Great it became part of the Greco-Bactrian Kingdom, a successor state of Alexander's empire. Northern Tajikistan (the cities of Khujand and Panjakent) was part of Sogdia, a collection of city-states which was overrun by Scythians and Yuezhi nomadic tribes around 150 BCE. The Silk Road passed through the region and following the expedition of Chinese explorer Zhang Qian during the reign of Wudi (141–87 BCE) commercial relations between Han China and Sogdiana flourished. Sogdians played a major role in facilitating trade and also worked in other capacities, as farmers, carpetweavers, glassmakers, and woodcarvers.
Very little of modern Tajikistan was part of what empire?
A: unanswerable

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The coverage of the events by the media came under scrutiny during the relay. Chinese media coverage of the torch relay has been distinct in a number of ways from coverage elsewhere. Western reporters in Beijing have described Chinese media coverage as partial and censored (for example when Chinese media did not broadcast Reporters Without Borders' disruption of the torch lighting ceremony), whereas Chinese netizens have in turn accused Western media coverage of being biased. The French newspaper Libération was criticised by the Chinese State press agency Xinhua for its allegedly biased reporting; Xinhua suggested that Libération needed "a stinging slap in the face" for having "insulted the Olympic flame" and "supported a handful of saboteurs".
What organization interrupted the relay and was not broadcast by the Chinese media?
A:
Reporters Without Borders