It is time for margaret to give her baby his bath. the water is warm and she adds bubble bath to the water. when she puts her baby in the water, the baby splashes around and plays with the bubbles, and genuinely appears to enjoy himself because his is/are being stimulated.

The correct answer is sense organs. 

When a baby is having a bath, several of his sense organs are being stimulated simultaneously, which is generally enjoyable for babies since they have a keen sense of curiosity and take delight in exploring new stimuli and sensations. To specify, during a bath, the baby has visual stimuli to look at (bubbles, water, etc.), pleasant fragrances (from the soap) and sounds (splashing).

What document are you referring to

Cextra