(a)in case of a person having income from business or profession,––(i)on or before the due date specified under section 263(1) for furnishing the returns of income for such tax year;(ii)such option, once exercised, shall apply to subsequent tax years;(iii)such option, once exercised, may be withdrawn only once for a tax year other than the tax year for which it was exercised; and(iv)after such withdrawal, the person shall never be eligible to exercise the option under this sub-section, except where such person ceases to have any income from business or profession, and in such a case the option under clause (b) shall be available;