Answer:
imitating her vocal and facial expressions
Step-by-step explanation:
The synchrony refers to the responsiveness of the mother, and the children to each other with respect to the emotional state. It is a combination of the behavior, emotional attached, biological attached with the children to their parents
According to the given situation, Victor and Rosa wants to enhance their synchrony with their 6 months old daughter so it can be done by her vocal and facial expressions
Hence, the first option is correct