#### Answer

a) in 1,050,501km underline all zeroes;
b) in 0.0020m cross out first 3 zeroes and underline last zero;
c) in 0.000000000000002s cross out all zeroes;
d) in 0.001090 cm cross out first 3 zeroes and underline last 2 zeroes

#### Work Step by Step

The first 3 zeroes are insignificant because they are leading zeroes (zeroes in front of (to the left of) a non-zero number that serve as a place holder). The last zero is significant because it is a trailing zero (to the right of a non-zero number after a decimal point).