Answer:
Atomic number = 10
Mass number = 20
Explanation:
Mass number = neutrons+protons
Mass number = 10+10 = 20
Answer: two elements and three atoms
Explanation:
An element is the simplest substance and hence cannot be broken down using chemical reactions.
Magnesium chloride 
is an ionic compound formed by the transfer of electrons from element magnesium (Mg) to element chlorine (Cl) where Magmesium forms a cation 
by losing two electrons and chlorine forms an anion 
by gaining electron.
There are 3 atoms in Magnesium chloride which include one atom of magnesium (Mg) and two atoms of chlorine (Cl).
Inquiring, which comes from the word inquiry which means, "an act of asking a question". In science, the first part of the scientific method is asking questions about the world around you and then after that, conducting experiments to get answers.
Answer : The correct option is, C.
Explanation :
pH meter : It is an electric device which measure the concentration of hydrogen-ion in the solution. It also measure the acidity or alkalinity of water in the solution.
Therefore, the purpose of student for testing the lake water is to understand how people use it in their daily-life. As this will help him to analyse the quality of lake water whether, it is fit for use or not.
Is water because a fish in order to survive it needs water
