See below for a possible answer. Note that one of the sentences (“While the outer stem is often tough…”) has been moved to a more logical position in the information flow:
Preparation
In the United States, large globe artichokes are frequently prepared by removing all but 5–10 mm of the stem. Sometimes they may have thorns which can interfere with eating. To remove thorns, around a quarter of each scale can be cut off.
Cooking
To cook, the artichoke is boiled or steamed. A cooked, unseasoned artichoke has a delicate flavour. Salt may be added to the water if boiling artichokes.
Preventing browning
Covered artichokes, in particular those that have been cut, can turn brown due to enzymatic browning and chlorophyll oxidation. Placing them in water slightly acidified with vinegar or lemon juice can prevent the discoloration.
Eating an artichoke
Leaves are often removed one at a time, and the fleshy base eaten with hollandaise, vinegar, butter, mayonnaise, aioli, lemon juice, or other sauces. The fibrous upper part of each leaf is usually discarded. The heart is eaten when the inedible choke has been peeled away from the base and discarded. While the outer stem is often tough and bitter, the core of the stem tastes similar to the artichoke heart, and is edible. The thin leaves covering the choke are also edible.
Note that a lot more could be done to convert the text above to plain language. For example, the entire passage is written in the passive voice. Try changing it to the active voice and revising the text further after you complete Exercise Nine.