chem quiz

i got the following questions wrong and cant seem to get the answers.please help me. thanks in advance


1.Daltons atomic theory explained the observation that the percentage by mass of the elements in a compound is always the same,thus Dalton's atomic theory supports what law
a.law of definiate composition
b . the law of conservation of mass
c   law of conservation of energy
d. law of multiple proportions
e.  law of chemical compounds


2. which of the following statements about isotopes is / are correct
i have different masses
ii have different number of neutrons
iii have different electrical charges
iv have different neuclear symbols
v have different mass numbers