Fill in the blank with the correct phrasal verb so that the sentence clearly expresses a daily telephone call: Sanjay __________ his mother in the morning every day.

Introduction / Context:
This item checks your understanding of phrasal verbs formed with the verb "call". The context is a daily action, where Sanjay contacts his mother in the morning. In everyday English, there is a specific phrasal verb that means "telephone someone", and you must select that exact form so that the sentence becomes natural and idiomatic.

Given Data / Assumptions:

• The sentence is "Sanjay __________ his mother in the morning every day."
• The options are "calls in", "calls up", "calls off", and "calls down".
• We are told by context that Sanjay regularly gets in touch with his mother in the morning.
• The missing word should produce a phrasal verb meaning "telephone" or "speak to by phone".

Concept / Approach:
Phrasal verbs often have meanings that cannot be guessed simply from the meanings of individual words. In Indian and international English, "call up" is a common phrasal verb meaning "to telephone someone". The other combinations "call in", "call off", and "call down" have different meanings that do not match the context of a regular friendly contact with a family member.

Step-by-Step Solution:
Step 1: Interpret the sentence. It talks about a repeated daily action involving Sanjay and his mother in the morning.Step 2: Recall the meaning of "call up". It means "to telephone someone" or "to make a phone call to someone".Step 3: Insert "calls up" in the blank: "Sanjay calls up his mother in the morning every day." This is a natural and very common expression.Step 4: Examine "calls in". This usually means "to visit briefly" or "to phone a message in", as in "He called in at the office", which does not fit the clear and direct sense of telephoning his mother.Step 5: Examine "calls off". This means "to cancel", as in "They called off the match", which is not correct here.Step 6: Examine "calls down". This is rarely used in modern English and can mean to rebuke or call something down, which again does not match the intended meaning.Step 7: Therefore, "calls up" is the only option that fits both grammar and meaning.

Verification / Alternative check:
To verify, think of similar sentences: "I call up my parents every Sunday", "Please call me up tonight", or "She called up her friend to share the news". These are well established patterns. The other options either change the meaning completely (cancel, rebuke) or create an awkward expression that does not match simple, everyday telephone contact.

Why Other Options Are Wrong:
Option A, "calls in", would change the meaning to "visits briefly" or "phones an office or radio show", which does not fit the idea of calling one's mother every morning.
Option C, "calls off", clearly means "cancels something", which is unrelated to a routine friendly call.
Option D, "calls down", is not used in this context and typically has a sense of reprimanding or calling something down, so it is inappropriate here.

Common Pitfalls:
Many learners confuse similar looking phrasal verbs because they focus on the main verb and ignore the particle. Another pitfall is to over generalise a meaning, thinking that any "call plus particle" can mean "telephone". In reality, English phrasal verbs need to be learned as fixed expressions. Remembering common everyday phrases like "call up your mother" helps avoid such errors in the exam.

Final Answer:
The correct expression is "calls up", so the answer is option B.