The answer from this questions is the letter
B. He should not use his opinions as evidence.
The minerals in hard water react with soap and affect its cleaning capacity. It's still possible to use hard water when washing by using more soap. The additional soap will no longer be affected by the minerals in the water, so they can clean just as effectively, but you'll be wasting more soap this way.
This assumption is not valid because, there are some elements which exist in two or more forms; they have the same atomic number but differ in their mass number, which meas that they possess different number of neutrons. These type of element are called isotopes. Isotope have the same atomic number and similar physical and chemical properties but they have different number of neutrons and therefore possess different masses.
I believe it is a crystal, read it in a chemistry book over last summer so might be off
<span>the loss of one or more electrons & the addition of one of more electrons</span>
