bacterium

"While walking to school, Sarah found a lost wallet on the ground. "

"My grandfather played a single of Elvis Presley at the family gathering. "

"The single-celled organism was studied by the biology students in their science class. "

"The student used a microscope to see the tiny cells in the plant leaf. "

"The old city had strong walls to protect it from enemies. "

"Just like a factory has specialized machines for different tasks, a cell contains organelles that each perform a specific job, such as creating energy or storing waste. "

"a blood sample"

"He examined the crime scene for clues."

"The under-the-counter storage bin kept the extra supplies hidden. "

"The nucleus of the family's discussions was always about who would do the dishes. "

"The scientist studied the effects of different types of soil on plant growth. "

"The school is located just outside the town, without the main shopping area. "