There was a time when a C meant average. The average GPA at four-year colleges and universities has risen from 2.52 in the 1950s to 3.11 in 2006. And according to Stuart Rojstaczer, a former Duke University professor and founder of GradeInflation.com, GPAs only keep rising. At some colleges, Rojstaczer says, over 50% of the grades given are A's.
Trench warfare was caused by an advance in defensive weaponry. The machine gun was too heavy to be used as a mobile weapon, and therefore was placed into a fixed position. Barbed and concertina wire was also heavily used.
It had been widely practiced in the US Civil War, the Russian-Japanese war and other fairly recent wars. Trench warfare of the First World War can be said to have begun in September 1914 and ended when the Allies made a breakthrough attack that began in late July 1918. Before and after those dates were wars of movement: in between it was a war of entrenchment.