The correct way to represent 0.0035 kg by using scientific notation is 3.5 x 10^-3 kg.
Answer: He will earn $75 after 3 years.
Explanation: To calculate Simple Interest, we use the formula:
.....(1)
where, i = Simple Interest
P = Principle amount
R = Rate of interest
t = Time period
Given:
P = $500
R = 5%
t = semiannually which means 
years
As we are asked the total amount earned after 3 years which means 6 half years, so we multiply the interest calculated semiannually by 6 to get the total interest after 3 years.
Putting all the values in equation 1, we get
i = $75
Total amount earned after 3 years = i = $75
= $75
The right answer is C.
Oxidation is the loss of electrons. A loss of electrons will appear as an increase in the positive charge of the element as it is converted to an ion. Here we have aluminum have an oxidation state equals zero as a reactant because it is in the element state. After reacting, it combines with three atoms chlorine where each chlorine atom usually has an oxidation state equals -1, therefore, we have -3 charges which have to be neutralized with the 3+ charges of aluminum.
To convert a number without the use of the expression 10^-4 you would have to treat it like an integer line for instance on an integer line the negative is to the left and the positive number is to the right so 3.91*10^-4 means that the decimal would have to move 4 places to the left so the answer would be .000391 instead of 3.91*10^-4.
I hope this helps you :)
