How many significant figures in 1. 19.99 2. 140486 3. 0.0609 3. 5.08 ?

1. 4 significant numbers

2. 6 significant numbers

3. 3 significant numbers

4. 3 significant numbers

Significant numbers are numbers obtained from the measurement results of exact numbers and the last number estimated  

1. 19.99

all non-zero numbers are significant numbers , so there are 4 significant numbers

2. 140486

a zero which is located between two non-zero numbers including a significant number , so there are 6 significant numbers

3. 0.0609

a zero in front of a decimal point is not a significant number, so there are 3 significant numbers (6,0 and 9)

4. 5.08

Any zeros between two non-zero numbers are significant, so there are 3 significant numbers(5,0 and 8)

it's c. elements are placed in rows based on how may valencies electrons have.

i need mutiple choices