Which sentence requires a comma between the underlined words?

Answer options with 4 options

1. 
   

Many ,begin underline,early childhood,end underline, memories are stored in the brain.

1. 
   

The ,begin underline,unlimited learning,end underline, abilities of the brain are amazing.

1. 
   

Trying new experiences makes a ,begin underline,stronger healthier,end underline, brain.

1. 
   

The brain works faster than some ,begin underline,large modern,end underline, computers.