Out of the following options, select the meaning of the idiom "out of date".

Introduction / Context:
This idiom question aims to check your understanding of the phrase out of date. The expression is commonly used to describe things that are no longer current, fashionable, or valid. Your task is to pick the option that most accurately reflects this sense of being old or no longer appropriate for the present time.

Given Data / Assumptions:

- Idiom: out of date. - Options express ideas related to time pressure, schedules, relationships, and fashion. - The idiom can refer to fashion, ideas, technology, or official documents. - The correct choice must match the idea of being no longer current.

Concept / Approach:
Out of date usually means old-fashioned or no longer up to current standards. For example, clothes may be out of date, meaning not fashionable, or software may be out of date, meaning it has not been updated. In some contexts, documents that have expired can also be described as out of date. The right option should therefore capture the idea of being old or outdated rather than simply being busy or missing a schedule.

Step-by-Step Solution:
Step 1: Recall sentences like His ideas are out of date or This phone is completely out of date. Step 2: Observe that in these sentences the phrase means old, obsolete, or not suited to current times. Step 3: Examine option D, Old-fashioned, which directly matches this meaning and can be used in similar contexts. Step 4: Check option A, Not have time; very busy, which refers to a person's schedule, not to the age of ideas or objects. Step 5: Look at option B, Not stick to the schedule, which concerns punctuality or planning and is unrelated to being outdated. Step 6: Consider option C, Fail to find a partner, which relates to social relationships and does not reflect the idiom's meaning. Therefore, option D is correct.

Verification / Alternative check:
Replace the idiom in a test sentence: The syllabus is out of date. Using option D gives The syllabus is old-fashioned, which means it no longer meets modern requirements and fits the context. Substituting the other options results in confusing or meaningless sentences. For example, The syllabus is not have time; very busy or The syllabus is fail to find a partner are clearly incorrect.

Why Other Options Are Wrong:
Option A refers to a person being busy, not to the currency or fashion of objects or ideas. Option B addresses not sticking to a timetable, which is completely different. Option C talks about failing to find a partner, which is unrelated to time based relevance or style. None of these options mention age, fashion, or validity, which are central to the idiom out of date.

Common Pitfalls:
Sometimes learners confuse out of date with out of time or behind schedule, especially when they see the word date and think of calendar dates. Remember that out of time refers to running out of available time, while out of date refers to being old and no longer current. Paying attention to the nouns around the idiom, such as ideas, fashions, documents, or machines, will help you recall the correct meaning quickly.

Final Answer:
Old-fashioned is the correct meaning of the idiom out of date.