Step 1: Identify the time expression.
The phrase “very soon” refers to the near future, not to completion before a future point.
Step 2: Choose the appropriate tense.
For a simple prediction or statement about the future, we use the
simple future tense:
\[
\text{will + base form of verb}
\]
Step 3: Analyse the options.
arrive — incorrect; auxiliary verb is missing.
will have arrived — future perfect; requires a specific future reference point.
will arrive — correct for a near-future event.
both will have arrived and will arrive — incorrect; both are not suitable here.
Hence, the correct answer is
\[
\boxed{\text{will arrive}}
\]