What are the keywords in the following sentence? volcanic activity under meromictic lake produced a cloud of carbon dioxide that asphyxiated villagers
activity, asphyxiate, cloud, dioxide, lake

What are the keywords in the following sentence? small waterfall and mossy rocks in a deep forest on a summer day
day, forest, rock

What are the keywords in the following sentence? looking across the mass of blooming flowers .
bloom, flower, look

What are the keywords in the following sentence? shadows move across a group of golden larch trees contrasted against blue skies
contrast, sky, tree