Which of the following is an incorrect statement for periodic abstinence?

• A
  The couple should abstain from coitus from day $10$ to $17$ of the menstrual cycle when ovulation could be expected.
• B
  $10^{th}$ to $17^{th}$ day of the cycle is the fertile period,when the chances of fertilization are high.
• C
  This prevents the chances of union of male and female gametes.
• D
  In this method,the ovum and sperms are prevented from physically meeting with the help of barriers.