Well,
For the first one, the answer would be C, because all organisms in Kingdom Animalia must eat in order to survive.
For the second one, all of the options are in Kingdom Animalia, but worms (A) and clams (C) are invertebrates. So that leaves options B and D.
Answer: Equal number of protons and electrons. Example: an atom of oxygen atom has 8 electrons and 8 protons and is neutral.
Explanation:
An atom that has no charge is a neutral atom. It contains electrons equal to protons. For example: A neutral atom of oxygen has 8 protons and 8 electrons.
An atom which has charge is said be ionized. It is either positively charged or negatively charged. It is positively charge when the number of electrons is less than the number of protons. For example: 
contains 10 electrons and 11 protons.
And when the number of electrons is greater than the number of protons, the atom is negatively charged. For example, 
has 17 protons and 18 electrons. It readily accepts an electron to complete its octet.
Answer:
A & D
Explanation:
A single-displacement reaction is a chemical reaction whereby one element is substituted for another one in a compound and thereby generating a new element and also a new compound as products.
From the options, only options A & D fits this definition of single-displacement reactions.
For option D: Both left and hand and right hand sides each have one element and one compound. We can see that K is substituted from KBr to join Cl to form KCl and Br2 on the right hand side.
For option A: Both left and hand and right hand sides each have one element and one compound. We can see that OH is substituted from 2H2O to join Mg to form Mg(OH)2 and H2 on the right hand side.
The other options are not correct because they don't involve only and element and a compound on each side of the reaction.
Yes because mercury has more protons and electrons that tin. (30 more)
