General particle physics question - AS

So i was doing a question and it comes up with the following question:

The equation represents the weak interaction between a negative pion and proton.

Negative pion + proton = Neutron Kaon + Particle x

4 Options:

Option 1 for particle x:
Charge: 0
Baryon number: 0
Strangeness: 0

Option 2:
Charge: 0
Baryon number: 1
Strangeness: +1

Option 3
Charge: 1
Baryon number: 1
Strangeness: 0

Option 4:
Charge: 0
Baryon number: 1
Strangeness: -1

So from there I narrowed it down to option 2 or 4. As its weak I know that strangeness isn't conserved. But my question is this. How do you know what quark structure to use for the neutron kaon?

As the kaon has 2 quark structures (anti down, strange) and (down, anti strange). But don't know what to use? (the answer on the mark scheme just says D)

Thank you!

The Kaon 0 is down, antistrange and the Anti-Kaon 0 is strange, antidown. This is a little fact that you might be expected to know.

However, this doesn't provide any further information for the question. I remember doing an AQA mock and this question did not provide enough information to distinguish from two options so I don't think that you can actually answer it