Fill in the Blanks

 Hamburgers need not be a product of (in the manufacturing sense) but definitely a product at (in the selling sense).

The phrasal verb 'give up' means to stop doing something, especially a habit like smoking. 'Give up smoking' means to quit or stop the smoking habit. 'Give in' means to surrender, 'give to' indicates transfer, and 'give off' means to release or emit - none of which mean quitting a habit.

'Beside' means at the side of or next to, which correctly describes Joan's position relative to the car. 'Besides' is incorrect - it means 'in addition to' or 'also', not physically next to something.

'Burst into tears' is the correct idiomatic expression meaning to suddenly start crying. 'Burst in tears' and 'burst with tears' are not standard English phrases for this meaning.

'Learn by heart' is the correct idiomatic expression meaning to memorize something completely. Other prepositions like 'to', 'in', or 'with' don't form this standard phrase.

'Gone through' means to read, examine, or review something completely. This matches the context of having read the book. 'Gone into' would suggest entering something, 'gone over' means reviewing but is less common for books, and 'gone to' doesn't fit.

'In the afternoon' is the correct preposition for times of day. We say 'in the morning', 'in the afternoon', and 'in the evening'. 'On' is used with specific days, not general times of day.

'Under observation' is the correct phrase meaning someone is being watched or monitored, especially in medical contexts. 'On observation' is not standard English for this meaning.

'In the end' means eventually, after everything has been considered, or finally. 'At the end' refers to a specific endpoint, but 'in the end' is the correct idiom for the final outcome of a situation.

'Within an hour' means in less than or equal to one hour, which fits the context of a promise to call back. 'In an hour' could work but 'within' better captures the sense of a time limit. 'By an hour' is incorrect usage.

'During the performance' is the correct phrase when referring to something that happened while the performance was ongoing. 'In the performance' could work but 'during' is more precise for events happening throughout an activity.

'At sea' is the correct phrase when someone is on a voyage on the ocean. While ships sail 'on the sea', people are 'at sea' when they're on maritime journeys. This is idiomatic usage.

 on the left means on the left hand side.

'For sale' is the correct idiomatic expression when something is being offered to be bought. 'On sale' means being sold at a discounted price. 'To sale' and 'with sale' are grammatically incorrect.

'Horrified at the sight' is the correct phrase. We use 'at' with emotional reactions to things we see or experience. 'Horrified by' could also work, but 'at' is more common with 'sight'. 'Horrified on' and 'horrified of' are incorrect.