What are different grades of reagent?

Why ddt is mostly found in tertiary or top consumers? Given all the different time zones across the globe and international date line how many hours can a calendar date have? What causes the temperatures at the north and south poles to remain so cold? What happens when both ends of a magnet meet? What is the difference between volcanic cones and volcanic plateaus? What would occur if cells were in mitosis more than interphase? Why might sandstone act as a reservoir for groundwater or oil while shale would not? What are the levels of organization from general to specific? Where is the world's tallest elevator located? What are the satellites of Mercury? What is paraphernal property? What two jobs do all ecosystems share? What direction does lines of latitude or parallels measure ditances? Field mice are sexually-reproducing organisms. In a population of field mice traits that promote survival and reproduction are likely to over time. Traits that do not promote survival and reproduction? What is the notion of time in different religious traditions? Which type of sensory information does the auditory system convert into neural impulse? What are the green alternatives to pewter? What limits scientists from downsizing the tokamak reactor? Why does China get to increase CO2 under Kyoto? If gene expression control occurs after transcription when did it occur after RNA was synthesized while RNA was synthesized while proteins are synthesized after proteins are synthesized?