The filament of spirogyra were put into equal volumes of sugar solutions X and Y. After 5 minutes, filaments from solution X had their cells contents rounded up while those from Y were unaffected. The experiment shows that

• A.solution X was stronger than Y
• B.solution Y was stronger than X
• C.Spirogyra used up the sugar in solution X
• D.solution X is good for stimulating sexual reproduction in Spirogyra
• E.solution Y was less contaminated than X