In an effort to protect seeds, farmers would often place scarecrows in fields. What kind of phrase is highlighted?

Corn, a plant that has several thousand varieties, is an important crop. What kind of phrase is highlighted?

A stalk of corn can grow up to twenty feet tall. What kind of phrase is highlighted?

Eating corn on the cob is a common activity at some picnics. What kind of phrase is highlighted?

A clause is a group of words