Best telephoto lens for the pentax k 70?

Here is what the site says about that.

From Pentax K-70: Pentax K-70: A DSLR by Pentax with a 24.2-megapixel APS-C sensor, announced in 2016. Weather-sealed, with a flip-out screen; the KF is a near-identical refresh of it. Specs - Maker: Pentax - Mount: Pentax K - Sensor: APS-C, 23.5 x 15.6mm, crop factor 1.5 - Resolution: 24.2 megapixels - Stabilisation: in the body - Announced: 2016 - Type: DSLR Focal lengths on it Lenses frame like 1.5 times their focal length on ...

From Pentax HD D FA 70-210mm f/4 ED SDM WR: Pentax HD D FA 70-210mm f/4 ED SDM WR: A zoom lens by Pentax for Full frame cameras, 70-210mm f/4. A lighter alternative to the f/2.8 telephoto zoom.

Quoted from this site's pages.