Your answer is
One of the most effective methods that can be used by researchers to avoid sampling bias is simple random sampling, in which samples are chosen strictly by chance. This provides equal odds for every member of the population to be chosen as a participant in the study at hand.
it is trapped beneath non porous rocks
Answer: The water cycle, also known as the hydrologic cycle, describes the process of how water moves through Earth's environment. In general, water evaporates from oceans, then it condenses in the atmosphere as water vapor cools. When enough water gathers in clouds, it precipitates back to the Earth's surface as rain, hail, snow or sleet.
I'll say that it is +1 since hydrogen is desperate to lose an electron to fulfill the octave rule (that the molecules want to gain 8 electrons and if they can't do it, they want to lose all their electron). Electron is - so if it lose a electron, it becomes +.
Hopefully this helps.
PS. I'm not certain of my answer but it is logical.
