If in a garden, there are 20 sunflower plants last year and through r…

The correct answer is Option (3) → 0.4 offspring per sunflower per year

A birth rate is a per capita rate: the number of new individuals is divided by the number of individuals that were already there, not by the new total.

Here, 20 sunflower plants were present last year and 8 new plants were added by reproduction.

Birth rate = new plants ÷ plants present last year = 8 ÷ 20 = 0.4 offspring per sunflower per year.

A common slip is to divide by the new total (8 ÷ 28, about 0.29), which matches none of the options. The calculation follows the book’s own lotus example, which uses the same numbers.

NCERT Extract:
Population Attributes – “… An individual may have births and deaths, but a population has birth rates and death rates. In a population these rates refer to per capita births and deaths. The rates, hence, expressed are change in numbers (increase or decrease) with respect to members of the population. Here is an example. If in a pond there were 20 lotus plants last year and through reproduction 8 new plants are added, taking the current population to 28, we calculate the birth rate as 8/20 = 0.4 offspring per lotus per year.”