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

(select all the correct choose each statement that is scientific. - the opinions of randomly selected participants in a survey prove the idea that global temperatures are not increasing on earth. - the universe's average temperature and rate of expansion support the idea that it began as one super-dense and hot mass 13.8 billion years ago. - ocean tides are caused by the uneven gravitational pulls of the moon and sun on different parts of earth. - human life is more valuable than other forms of life on earth because humans are more intelligent than other organisms.