Question

how to print all lines between
“section B (”
To the next “section” word that begin in line?

section A (

.
.

)

section B (

.
.

)

section C (

.
.

)

Answer 1

If you want to print everything from “section B” to “section C” including those lines,

sed -ne '/^section B/,/^section/p'

If you don’t want to print the two “section” lines,

sed -e '1,/^section B/d' -e '/^section/,$d'

If you want to include “section B” and the closing parenthesis (but not “section C”),

sed -ne '/^section B/,/^)/p'

And there are a few other possible variants.