Final answer:
The birth rate in a population of lotus plants is calculated by dividing the total number of new plants by the initial population. The correct birth rate per lotus per year is 0.4, making the answer D.
Step-by-step explanation:
The birth rate can be calculated by dividing the number of offspring produced by the initial population. In the given scenario, a pond had 20 lotus plants last year and through reproduction, added 8 new plants. This makes the current population 28. To find the birth rate, we divide the number of new plants (8) by the initial number of plants (20).
The birth rate per lotus per year is therefore 8 ÷ 20 = 0.4. This means each lotus, on average, produced 0.4 offspring over the course of a year.
Therefore, the correct answer is D. 0.4 offspring per lotus per year.