Best telephoto lens for the pentax k 500?

Here is what the site says about that.

From Pentax K-500: Pentax K-500: A DSLR by Pentax with a 16.3-megapixel APS-C sensor, announced in 2013. The K-50 without weather sealing. Specs - Maker: Pentax - Mount: Pentax K - Sensor: APS-C, 23.5 x 15.6mm, crop factor 1.5 - Resolution: 16.3 megapixels - Stabilisation: in the body - Announced: 2013 - Type: DSLR Focal lengths on it Lenses frame like 1.5 times their focal length on full frame: 16mm like 24mm, 23mm like 35mm, ...

From Wildlife and sport: Shutter speed: To freeze motion: about 1/500s for people running, 1/1000s for most sport, 1/2000s or faster for birds in flight. That pushes ISO up, so a body that stays clean at high ISO matters, and so does modern noise reduction software.

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