Which number in written in scientific notation? (big points reward)

a: 7.8 x 10^-5
b: 3.2 x 100^2
c: -5 x 10^-12
d: 0.84 x 10^6

Will gve pints stars and brainliest

You have 17 cats that live in houses on your street, 24 dogs, 3 fish, and 4 hamsters. what percent of animals on your block are dogs?

Afrequency table of grades has five classes (a, b, c, d, f) with frequencies of 3, 13, 14, 5, and 3 respectively. using percentages, what are the relative frequencies of the five classes?