In order to increase gross motor development indoors, a teacher might add: a. rollers to the paint easel. b. scissors to the art area. c. cookie cutters to the clay area. d. pegboards at the manipulative table

The best option to increase gross motor development indoors would be "a. rollers to the paint easel." Gross motor skills involve the larger muscles in the arms, legs, and torso. Gross motor activities include walking, running, throwing, lifting, kicking, etc. These skills also relate to body awareness, reaction speed, balance and strength.

Here is why the other options are not as suitable:

b. Scissors to the art area: This would help in developing fine motor skills as it involves precision and small muscle movements.

c. Cookie cutters to the clay area: This also involves more of fine motor skills as it requires precision to use cookie cutters properly.

d. Pegboards at the manipulative table: This would also be more related to fine motor skills as it involves precise hand-eye coordination to place the pegs in the correct spots.

So, adding rollers to the paint easel would require larger movements from the arm and torso, thus helping in the development of gross motor skills.