Assertion (A) : Mangrove have specialized above ground roots called breathing roots or pneumatophores.

Reason (R) : These roots have numerous pores through which oxygen enters into the underground tissues.

Mangrove have specialized above ground roots called breathing roots or pneumatophores. since mangroves are found in deltaic regions where the roots are generally submerged in water, the trees root system develop pneumatophores that help in breathing.

Pneumatophores have numerous pores through which oxygen enters into the underground tissues.

Thus, correct option is B.