This is a single choice question; skip ahead to question content incorrect correct answeryour answer a bx c d time spent: 1 min 59 secs content & skills cc5dfc5bchsirs1 what causes duplex dna with a certain (a + t): (g + c) ratio to melt at a higher temperature than comparable length duplex dna with a greater (a + t): (g + c) ratio? a. stronger van der waals forces of pyrimidines b. stronger van der waals forces of purines c. increased π- stacking strength d. reduced electrostatic repulsion of phosphates