Understanding Sentence Completion: Friend's Birthday Scenario

This question tests our knowledge of correct adverb placement and common idiomatic phrases in English. We need to fill in the blanks to make the sentence grammatically correct and meaningful, specifically relating to forgetting a friend's birthday and figuring out how to make it up to him.

Analyzing the First Blank: Adverb Placement

The first blank modifies the verb "forgot". We have two options for the adverb and verb combination:

• completely forgot: Here, the adverb "completely" comes before the verb "forgot". This placement is very common and natural in English, emphasizing the totality of the forgetting.
• forgot completely: Here, the adverb "completely" comes after the verb "forgot". While grammatically possible, it can sometimes sound slightly less natural or emphasize the *manner* of forgetting rather than the completeness of the act itself. In the context of a birthday, emphasizing the complete oversight is more typical.

Both placements are technically correct, but completely forgot is often preferred for emphasis in this type of context.

Analyzing the Second Blank: Idiomatic Phrasing

The second blank relates to not knowing how to compensate the friend. We have two options:

• don’t just know: This phrasing is awkward and doesn't convey the intended meaning. It suggests that knowing is not the only thing they do, which doesn't fit the context of needing a solution.
• just don’t know: This is the standard, idiomatic way to say someone has no idea or lacks knowledge about how to do something. It perfectly fits the situation where the speaker needs to figure out how to apologize or compensate their friend.

Determining the Correct Answer

Based on the analysis:

• The first blank is best filled with completely forgot for natural emphasis.
• The second blank must be just don’t know to convey the intended meaning idiomatically.

Therefore, the correct combination is completely forgot --- just don’t know.

Final Sentence Construction

Putting it together, the sentence reads: "We completely forgot our friend’s birthday and we just don’t know how to make it up to him." This accurately reflects the situation described.