technetium-99m is used as radioactive tracer for certain medical tests. It has a half-life of 1 day. Consider the function T where T(d) = 100(2)^-d is the percent of technetium-99m remaining d days after the test. Which expression represents the number of days until only 5% remains? A) log20 2. B) -log2 20. C) log2 (1/20). D) -log2 (1/20).