Pick out the bacteria that are useful to humans. Choose all answers that apply. A Soil bacteria B Colon bacteria C Infectious bacteria C D Cyanobacteria

## Step 1<br />The problem asks us to identify the types of bacteria that are beneficial to humans. The options provided are soil bacteria, colon bacteria, infectious bacteria, and cyanobacteria.<br /><br />## Step 2<br />Soil bacteria (option A) are beneficial to humans as they play a crucial role in nutrient cycling and maintaining soil health. They help in the decomposition of organic matter, which in turn enriches the soil with nutrients.<br /><br />## Step 3<br />Colon bacteria (option B) are also beneficial to humans. They are part of the normal flora of the human gut and play a vital role in digestion and nutrient absorption.<br /><br />## Step 4<br />Infectious bacteria (option C) are not beneficial to humans. They cause diseases and are therefore harmful.<br /><br />## Step 5<br />Cyanobacteria (option D) are beneficial to humans as they are a source of oxygen and are used in the production of certain foods and medicines.