<prompt> Pedzisa mutsara unotevera: Margretta Gretta Kok akaberekwa musi wa16 Gumiguru 1944, muAmsterdam mutambi wechiDutch akasiya basa uyo akapinda mumitambo yeOlympic yezhizha ya1960 na1964. Muna 1960, akanga ari wechishanu mumakwikwi e200m breaststroke, asi muna 1964 haana kusvika kumagumo. Muna 1966, akahwina menduru yegoridhe mu 4 × 100 m medley relay pa  <response>: Makwikwi eEuropean Aquatics. Munununa wake, Ada Kok, akanga ariwo mutambi wenhangemutange yeOlympic uye aivawo muchikwata chimwe chete ichocho chakahwina menduru yegoridhe mu 1966. 