Concept:Percentage composition of a species is found by dividing its count by the total population count and multiplying by 100.Explanation:The number of Imperata spp is 23.Total plant species counted is 15+5+7+23=50.So, percentage of Imperata spp is 5023×100%=46%.Thus, Imperata spp makes up 46% of the garden population.Answer:46% (Option C).