To Select, To Choose
する verb
選択 is "selection" or "choice." If you do the verb version of this, you are going to select or to choose.
せんたくする
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own. The reading also comes from 選択.
結婚相手にどちらの女性を選択するか決めましたか？
Have you decided which girl to choose as your marriage partner?