Compared to January, the sales of roses in July

Expenditure on roses in January = 1136916

Price of roses per dozen = 99

Roses sold = 1136916/99

                =11484 dozens

Expenditure on roses in July = 1188432

Price of roses per dozen = 144

Roses sold = 1188432/144

                =8253 dozens 

Sales of roses in July as compared to January = [(8253-11484)/11484]*100

                                                                    =  - 28.13%

Since Change is negative, there is a decrease of 28.13%.
Hence B is the correct answer.