The correct options are as follows:
1. B.
In scientific investigation, an hypothesis refers to a supposition that is put forward to explain an observed phenomenon. A hypothesis is described as valid if it fulfilled five different conditions. The conditions are as follows:
1. It must be capable of empirical verification.
2. It must be express clearly and it must be definite and certain.
3. It must be specific and it is predictions must be clearly expressed.
4. It must be formulated in such a way that its content can easily be translated to understand the observed phenomenon that give birth to the hypothesis.
5. It should possess theoretical relevance.
2. D.
Scientific investigations usually make use of two major variables, these are dependent variables an independent variables. The dependent variable refers to the variable whose value depend on that of another variable. The independent variable on the other hand refers to that variable whose variation does not depend on the value of another variable. In the question given above, the natures of the three substances is the independent variable because their variation is not determined by any variable.
3. B.
If a chemical plant near the source of a water body is dumping mercury inside the water, then the highest amount of mercury will be found at the mouth of the river while the lowest quantity of mercury will be found at the middle of the water. This is because as the water waves are carrying the mercury deposits away from the mouth of the river, they will disperse it evenly in the river and thus its concentration will reduce compare to that present at the mouth of the river. The highest amount of mercury is found at the mouth of the river because that is where the mercury enters the water.
