He left his speech on the plane and so was unable of giving his presentation; all the same he insisted to go to the conference.
A. unable
of giving his presentation; all the same he insisted to go
"unable to" is the correct IDIOM that is used. "to give" is the correct infinitive form of verb to be used. Hence incorrect.B. unable
to giving his presentation; all the same he insisted
on go"to give" is the correct infinitive form of verb to be used. "on going" is the correct form of verb to be used. Hence incorrect.C. unable of giving his presentation; all the same he insisted on going
"unable to" is the correct IDIOM that is used. "to give" is the correct infinitive form of verb to be used. Hence incorrect.D. unable to give his presentation; all the same he insisted on going
"unable to" is the correct IDIOM that is used. "on going" is the correct form of verb used. Hence correct.E. unable to give his presentation; all the same he insisted to going
"on going" is the correct form of verb to be used. Hence incorrect.