________ weed is the alternate weed host for ergot disease in pearl millet.

Correct option is A

Ergot disease is caused by Claviceps species.
The pathogen survives on alternate grass hosts.
Cenchrus ciliaris is a common grass weed.
It harbors ergot pathogen during off-season.
This helps disease carryover to pearl millet.
Other weeds are not major hosts.
Hence, Cenchrus ciliaris is correct.