<prompt> A couple presents with infeility. On investigation, the husband is found to have azoospermia on semen analysis. Vas was not palpable on per rectal examination. Semen had low volume, high viscosity and fructose was present. What will you do next?KaryotypePSATrans-rectal ultrasoundCFTR gene mutation analysis  <response>: Ans. d. CFTR gene mutation analysis 