Prepositions

in, on

Step 1: Identify the first blank - 'Mumbai' is a large city, so we use 'in' with cities. Step 2: Identify the second blank - 'third floor' refers to a surface/level, so we use 'on' with floors. Step 3: 'At' is used for small towns or specific addresses, not large cities like Mumbai. Step 4: We don't use 'in' with floors because floors are surfaces, not enclosed spaces. Step 5: The combination 'in, on' correctly shows location in a city and position on a floor level.

at

Step 1: Identify the time reference - '6:30 p.m.' is a specific point in time. Step 2: Remember that 'at' is used with specific times of the day. Step 3: 'In' is used with parts of the day (morning, evening) or longer periods, not specific times. Step 4: 'On' is used with days and dates, not clock times. Step 5: 'By' means 'not later than', which would change the meaning to 'before 6:30 p.m.' rather than exactly at that time.

on

Step 1: Visualize where books are typically placed - they sit on top of shelves. Step 2: 'On' is used for surfaces, and a shelf is a flat surface. Step 3: 'In' would suggest the book is enclosed within something, which doesn't apply to shelves. Step 4: 'At' is used for specific points or locations, not surfaces. Step 5: 'Under' would mean the book is beneath the shelf, which is not the typical placement.

to take care of

Step 1: Identify the phrasal verb 'look after' and its context with caring for a brother. Step 2: 'Look after' means to take care of or be responsible for someone. Step 3: 'Search for' would be 'look for', not 'look after', making this option incorrect. Step 4: 'Look behind' is a literal meaning that doesn't fit the phrasal verb context. Step 5: 'Follow someone' doesn't capture the caring, protective meaning of 'look after'.