Step 1 (Identify subject-verb agreement).
"The team" is a collective noun, generally treated as singular in American English when referring to it as a single unit. Step 2 (Check the verb form).
"have been" should be replaced with "has been" to match the singular subject. Step 3 (Corrected sentence).
"The team has been practicing every day for the upcoming tournament."
\[
{\text{have (Option (b)}}
\]