In the following sentence, the blank must be filled with a suitable preposition. Select the correct alternative: "The baby looked ________ the toffee with greedy eyes."

Introduction / Context:
This is a preposition question testing your familiarity with common verb-preposition combinations in English. The sentence describes a baby directing its gaze toward a toffee, emphasising the way it looked at the sweet. Choosing the correct preposition is essential for sounding natural and grammatically correct.

Given Data / Assumptions:

• Sentence: "The baby looked ________ the toffee with greedy eyes."
• Options: upon, into, on, at.
• The verb is "looked" and the object of gaze is "the toffee".
• We assume ordinary physical looking, not metaphorical meanings.

Concept / Approach:
In English, when we talk about directing our eyes towards something, we most often use the phrase "look at" followed by an object: "look at the sky", "look at the picture". Some prepositions like "into" and "upon" are also used with "look", but they change the nuance sharply ("look into" means investigate, "look upon" can mean consider in a certain way). For a simple description of a baby's gaze, the standard collocation is "looked at the toffee".

Step-by-Step Solution:
Step 1: Identify the basic meaning: the baby is directing its eyes towards the toffee, probably wanting to eat it. Step 2: Recall the normal expression: "look at something" for simply observing it. Step 3: Test "upon": "looked upon the toffee" sounds archaic and more like viewing something with an attitude, not just staring greedily at food. Step 4: Test "into": "looked into the toffee" would mean examining the inside of something or metaphorically investigating, which is clearly wrong here. Step 5: Test "on": "looked on the toffee" is not idiomatic; we generally say "looked on" meaning "watched as a bystander", usually followed by a different structure. Step 6: Test "at": "looked at the toffee with greedy eyes" perfectly expresses the idea and follows standard English usage. Step 7: Conclude that "at" is the correct preposition.

Verification / Alternative check:
Examples from everyday English confirm this pattern: "The child looked at the toy", "She looked at the cake longingly", "They looked at the painting in silence." All use "look at" to show gaze directed towards an object. In grammar guides, "look at" is listed as the default pattern for visual attention. This supports "at" as the only suitable choice among the options.

Why Other Options Are Wrong:

• upon: "Look upon" is more literary and often used metaphorically, as in "look upon him as a friend"; it does not fit a simple description of staring at food.
• into: "Look into" means investigate or examine a matter, for example, "look into the problem", not gaze at a visible object.
• on: "Look on" is used in phrases like "look on with interest" or "look on while others work", not "look on an object".

Common Pitfalls:
Students sometimes overcomplicate such questions by searching for unusual meanings of prepositions instead of trusting their sense of normal usage. Another issue is direct translation from mother tongues, which may use different prepositions. To avoid these mistakes, try to recall actual English sentences you have read or heard, and lean towards the simplest, most common collocation when describing everyday actions like looking at an object.

Final Answer:
The correct preposition is "at", so the sentence should read: "The baby looked at the toffee with greedy eyes."