The average age at which an infant can sit unattended is approximately months.
a. two to three
b. eight to nine
c. three to five
d. five to seven

The correct answer for the fill in the blank is D) Five to seven.

The average age at which an infant or a baby can sit without the help of others is approximately 5-7 months. At this age, the baby can independently hold his/ her neck and balances the body weight.

Thus, at an age of 5- 7 months, the infant can sit by own without anybody's help.

Therefore, option D) is the right answer.

answer; the correct answer is (beta)