DDT on exposure to water decomposes. It's half life is 10 years. How much time will it take for its 90% decomposition? a) 40yrs b)70yrs c) 500yrs d)700yrs​

How can a give a full method for the experiment of separating sand from water by filtration? 1-materials 2-steps 3-conclusion also for water and salt separated by the evaporation or distillation process

Which of the following is true about the speed of light? it depends on the wavelength.

Is the idea of spontaneous generation supported by redi's experiment? justify your answer in 2-3 sentences?