The correct option is A fifth
By the 5th week of pregnancy, the foetus grows rapidly and the major organs like the brain and heart develop.
By the 10th and 11th week (3rd month), the external features like limbs and digits are formed, the external genitalia develop and the placenta will be fully functional.
By the sixteenth week (2nd trimester), the taste buds develop and the foetus will gain the ability to hear.