Choose the most suitable option to fill in the blank.

The doctors recommended him to improve both his muscle gain ______ mass weight.

Correct option is D

Explanation:
The correct answer is and.

In the given sentence, two related ideas are being connected: muscle gain and mass weight. The correct conjunction to link these two similar objectives is "and", which is used to join words, phrases, or clauses of equal importance.

Information Booster:

"And" is used to join two similar or related ideas, actions, or things in a sentence.

Example: "She bought apples and oranges from the store."

In the given sentence, "muscle gain" and "mass weight" are both aspects of physical improvement, making "and" the best choice.

The sentence describes two aspects of the recommendation: muscle gain and weight gain.

"And" properly joins them as two connected goals of the doctor's advice.

Examples of Similar Usage:

"The athlete trained for strength and endurance."

"The nutritionist advised him to eat more protein and healthy fats."

Additional Knowledge:

As soon as:
This phrase is used to indicate time or immediacy, but the sentence does not describe an event that happens immediately after another.
Example: "Call me as soon as you arrive."

Although:
"Although" is a subordinating conjunction that introduces contrast between two ideas, which is not the case here.
Example: "Although he was tired, he continued to work out."

While:
"While" is used to show simultaneous actions or contrast, but the sentence is not describing two actions happening at the same time.
Example: "He listened to music while working out."