Ans. is 'a' i.e., Tolcapone o Both entacapone and tolcapone enhance and prolong the therapeutic effect of levodopa-carbidopa in advanced and fluctuating parkinsons disease. They may be used to smoothen off the 'wearing off', increase 'on' time and decrease loff' time, improve activities of daily living and allow levodopa dose to be reduced,o Treatment of on - off phenomenon in parkinsonism:Add one or two additional doses of levodopa.Continuous delivery of levodopa in duodenum.Avoid proteins in diet.Controlled release oral levodopa.'' peripheral decarboxylase inhibitor.Use of subcutaneous apomorphine.