Here's why:

* Krypton's boiling point is -153.4 °C. This means that at temperatures below -153.4 °C, krypton exists as a liquid.

* Krypton's melting point is -157.3 °C. This means that at temperatures below -157.3 °C, krypton exists as a solid.

Since -10 °C is significantly higher than krypton's boiling point, it will be a gas at that temperature.