A. The water you drink today could be the same water a dinosaur drank millions of years ago because the earth's water cycle, known as the hydrologic cycle, uses and continuously recycles our water.
The amount of water in clouds, on land, in ice caps, and in oceans is the same today as it was years and years ago. It will remain the same in the future. Water from land and oceans is warmed by the sun and evaporates into the air as a gas called water vapor. Water vapor and clouds containing water droplets and/or ice crystals can fall back to the earth as rain, snow, sleet, or hail. Some of it falls into the oceans, some may run off the land into lakes, rivers, and streams, and some filters into the soil to become groundwater. Water is returned to the atmosphere when plants transpire (or "breathe") and when water evaporates from the oceans, lakes, rivers, and streams.
This cycle of water is the process by which water changes forms, from groundwater to water vapor to precipitation and then repeats itself over and over. So there is no reason why the water we drink today was not the same water that dinosaurs drank millions of years ago.