Implantation or uterine attachment of the blastocyst presumably occurs between

• A
  $2^{nd}$ and $5^{th}$ days after ovulation
• B
  $5^{th}$ and $7^{th}$ days after ovulation
• C
  $7^{th}$ and $9^{th}$ days after ovulation
• D
  $9^{th}$ and $11^{th}$ days after ovulation