Anew recruit in the armed forces stands at attention on a hot afternoon. he decides to lock his knees, thinking it will make the standing easier. after a short while, he faints. what has occurred?

There are no options to choose from and this makes it hard to answer the question. I hope my answer is correct and comes to your help. The reason that the new recruit fainted was that he did not use muscular compression to return the blood to the heart and thus his brain became devoid of oxygenated blood, resulting in the new recruit getting fainted.

Ithink all of these events

1.wear safety goggles when heating or mixing substances 2.tie back long hair when doing experiment in order to prevent from catching fire or dipping into chemicals accidentally 3.keep all exits and passages clear4.wear laboratory coats