is concentrated on|was concentrated on|be concentrated on

该领域的投资高度集中在少数几家大公司上。

Investment in this sector ___is heavily ___concentrated ___on a few large companies.

文艺复兴时期，画家较少把注意力集中在宗教主题上。

During the Renaissance, painters' attention ___was ___concentrated ___on fewer religious themes.

化学课上，你的注意力应集中在实验上。

In chemistry class, your attention should ___be ___concentrated ___on the experiment.