A city of 200 residents has 100 black residents and 100 white residents. It is divided into two equal-sized neighborhoods. Neighborhood A has 90 white residents and 10 black residents, neighborhood B has 10 white residents and 90 black residents. Now suppose 10 white residents from neighborhood A and 10 black residents from neighborhood B leave the city. Which of the following statements is true about the city's dis-similarity index.

(a) The dis-similarity index becomes larger.

(b) The dis-similarity index becomes smaller.

(c) The dis-similarity index does not change.

(d) The change of dis-similarity index cannot be determined without knowing the destinations of these residents.