A particular strain of influenza is known to spread according to the function p(t) = (t2 + t) , where t is the number of days after the first appearance of the strain and p(t) is the percentage of the population that is infected. Find the instantaneous rate of change of p with respect to t at t = 4. A. 9% per day 4 O B. 5% per day 2 O C. 5% per day O D. 2% per day