The NRC appears to be a completely different exercise; how is it linked to the CAA?

Supporters of the Citizenship Amendment Act question why people should have any objections with the legislation on grounds of religious discrimination, since

1. It does not exclude any Muslim who is a genuine Indian citizen
2. It seeks to provide citizenship only to minorities from Muslim-majority nations, where the former are known to face persecution.

Those against the move argue that it is here that the Act needs to be read in conjunction with the NRC, for its true implications to be grasped. The NRC exercise in Assam showed that a large number of those excluded from the formal list were in fact Bengali Hindus. By relaxing the conditions for citizenship for members of the six communities mentioned, the CAA gives them a second chance to claim citizenship. 

This, opponents of the CAA argue, makes Muslims living in India vulnerable.If the NRC exercise is, in fact, extended to all parts of the country, all Muslims who lack of documentary evidence required for the NRC would be labelled illegal immigrants, burdened with the onus of proving their Indianness irrespective of how long they may have been residing in this country.

Similar fears also extend to other groups like Sri Lankan Tamil refugees who have been residing in Tamil Nadu for decades and are not covered by the latest amendments. And the Rohingyas, an ethnic group facing genocidal violence in their home country of Myanmar, who also are excluded from the CAA. In fact, the Home Minister has explicitly asserted that Rohingya refugees will never be granted citizenship in this country.