Can anyone finish this statement?

Question

Lack of expressing herself/himself due to lack of confidence to speak up due to lack of .......................

I say the blank is Experience..what do you think

Answer 1

I would say due to the lack of proficiency.

Answer 2

yeah, but how about, "failure to/hesitant to express him/herself because they lack the confidence to speak up due to lack of experience in the subject.

or somethin like that.  all the lack ofs sound wierd.

Answer 3

I think J is right "...lack of experience on the subject."