In humans,fertilization is only possible if:

• A
  The ovum and sperms are transported simultaneously to the ampullary-isthmic junction of the fallopian tube.
• B
  The ovum and sperms are transported simultaneously to the cervical-ampullary junction of the uterus.
• C
  Sperms are transported into the cervix within $48$ hours of the release of the ovum.
• D
  Sperms are transported into the vagina just after the ovum is released into the fallopian tube.