Step 1: Identify the time expression.
The word “tomorrow” refers to a definite time in the future.
Step 2: Choose the correct tense for a future action.
For a simple statement about what will happen in the future, we use the
simple future tense:
\[
\text{will + base form of verb}
\]
Step 3: Analyse each option.
will watch — correct simple future form.
watch — present tense; incorrect with “tomorrow”.
will have watched — future perfect; used only when an action is completed \emph{before} a future time.
both (A) and (C) — incorrect since (C) is not suitable here.
Step 4: Select the correct option.
Hence, the correct answer is
\[
\boxed{\text{will watch}}
\]