How to fill visa application form of P.R.China?

hi, i m vimal from nampula mozambique. i m filling visa form for apply visa. i want ask in visa form if they ask sex M or F, my sex is M what i have to sign in blank space x sign or true sign? and some questions that we no need to reply what we have to write in front of that question? we left blank space or we have to cross sign or we have to write -------N.A.--------?