I've just proof read a clinical study paper about deep brain stimulation and one of the authors says the 'it's' that I inserted (see below) should be its - he sounded so sure of himself. Who's wrong?
'Our results suggest that DBS of the EPN and CM-Pf exerts it?s therapeutic effect on Levodopa-induced dyskinesias in the 6-OHDA rat PD model independently from it?s effect on beta activity'