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.
Trench warfare was not an innovation of World War I, but it was never so prevalent in any other war before or since. One reason that World War I became a massive trench war on the Western Front was that western Europe was densely populated. The opposing armies in the west were so vast that they could be deployed across the entire European continent, forming a continuous front.