Questions: The very first and last step to every microbiology lab exercise is Multiple Choice to create a new stock culture to preserve organisms. to label and recheck the labels on your cultures. to remove or add materials to the incubator. to disinfect the lab bench. Prev 12 of 30

The answer is the fourth one: to disinfect the lab bench.

Explanation for each option:

1. To create a new stock culture to preserve organisms: This is not typically the first or last step in every microbiology lab exercise. Creating stock cultures is an important task but is usually done as needed, not as a routine step for every exercise.

2. To label and recheck the labels on your cultures: While labeling and rechecking labels is crucial for accuracy and avoiding contamination, it is not necessarily the very first or last step in every lab exercise. This step is usually performed during the handling and processing of cultures.

3. To remove or add materials to the incubator: This step is specific to certain procedures that require incubation. It is not a universal first or last step for all microbiology lab exercises.

4. To disinfect the lab bench: Disinfecting the lab bench is a critical step to ensure a sterile working environment and to prevent contamination. It is standard practice to disinfect the lab bench both at the beginning and at the end of a lab exercise to maintain cleanliness and safety.

Summary: The very first and last step to every microbiology lab exercise is to disinfect the lab bench. This ensures a sterile environment and prevents contamination, which is essential for accurate and safe microbiological work.