Article: During World War II, San Diego became a major hub of military and defense activity, due to the presence of so many military installations and defense manufacturers. The city's population grew rapidly during and after World War II, more than doubling between 1930 (147,995) and 1950 (333,865). During the final months of the war, the Japanese had a plan to target multiple U.S. cities for biological attack, starting with San Diego. The plan was called "Operation Cherry Blossoms at Night" and called for kamikaze planes filled with fleas infected with plague (Yersinia pestis) to crash into civilian population centers in the city, hoping to spread plague in the city and effectively kill tens of thousands of civilians. The plan was scheduled to launch on September 22, 1945, but was not carried out because Japan surrendered five weeks earlier.

Question: What were the Japanese originally going to drop on San Diego from their kamikaze planes?
Ans: fleas infected with plague (Yersinia pestis)


Article: Motors have very little room for electrical insulation so they generally have low voltage ratings. Because transformers (prior to the development of power electronics) cannot step down DC voltages, trains were supplied with a relatively low DC voltage that the motors can use directly. The most common DC voltages are listed in the previous section. Third (and fourth) rail systems almost always use voltages below 1 kV for safety reasons while overhead wires usually use higher voltages for efficiency. ("Low" voltage is relative; even 600 V can be instantly lethal when touched.)

Question: Why 1kV voltage is almost always used by rail systems?
Ans: safety reasons


Article: From all the fault gases formed in power transformers, hydrogen is the most common and is generated under most fault conditions; thus, formation of hydrogen is an early indication of serious problems in the transformer's life cycle.

Question: What is the most common gas found in power tranformers?
Ans: hydrogen


Article: Areas such as South Street and Old City have a vibrant night life. The Avenue of the Arts in Center City contains many restaurants and theaters, such as the Kimmel Center for the Performing Arts, which is home to the Philadelphia Orchestra, generally considered one of the top five orchestras in the United States, and the Academy of Music, the nation's oldest continually operating opera house, home to the Opera Company of Philadelphia and the Pennsylvania Ballet. The Wilma Theatre and Philadelphia Theatre Company have new buildings constructed in the last decade on the avenue. They produce a variety of new works. Several blocks to the east are the Walnut Street Theatre, America's oldest theatre and the largest subscription theater in the world; as well as the Lantern Theatre at St. Stephens Church, one of a number of smaller venues.

Question: What is the oldest theater in the U.S.?
Ans:
Walnut Street Theatre