To Stretch
intransitive verb, transitive verb, godan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means stretch so the verb version is to stretch.
はる
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: Imagine yourself trying to stretch (or better yet stand up and do it). Every time you stretch you start to laugh uncontrollably. HA (は) HA HA HA HA HA. Go ahead and laugh like that out loud while you stretch, it will help you to remember this reading.
バレーボールのネットを張ったのは誰ですか?
Who put up the volleyball net?