Meaning: 'Up' in this context means to enhance or improve the brightness or appearance of something, indicating that the gold patches make their heads look brighter.

Wrong options:

• down: 'Down' implies a decrease or reduction, which contradicts the idea of brightening and does not fit the positive context of the sentence.
• glow: 'Glow' is a verb and does not fit grammatically as it cannot function as an adverb modifying 'brighten' in this context.
• on: 'On' is a preposition that does not convey the intended meaning of enhancement and does not fit grammatically in this context.

Correct answer: seen

Explanation: The word 'seen' is the correct past participle form that fits grammatically and contextually, indicating that emperor penguins are rarely observed in subantarctic waters, aligning with the sentence's meaning.

Meaning: 'Seen' means to be observed or noticed, indicating that these penguins are not commonly found in those waters.

Wrong options:

• swim: 'Swim' is a verb that does not fit grammatically as it does not convey the idea of observation and is not in the correct form for this context.
• submerged: 'Submerged' suggests being underwater, which does not fit the context of visibility and observation in this sentence.
• floating: 'Floating' implies a state of being on the surface of the water, which does not align with the intended meaning of being rarely observed.

Correct answer: whilst

Explanation: The word 'whilst' serves as a conjunction that indicates simultaneous actions, fitting grammatically and contextually as it connects the act of incubating the egg with the female going to sea.

Meaning: 'Whilst' means 'during the time that' or 'at the same time as,' indicating that the female is away while the male incubates the egg.

Wrong options:

• rather: 'Rather' is an adverb that expresses preference and does not fit grammatically or contextually in this sentence.
• however: 'However' is a transitional word that introduces a contrast, which does not align with the context of simultaneous actions in this sentence.
• though: 'Though' is a conjunction that typically introduces a contrast or exception, which does not fit the intended meaning of concurrent actions.

Correct answer: covered

Explanation: The word 'covered' is the past participle that fits grammatically and contextually, indicating that the male penguin's feet are enveloped in skin and feathers, aligning with the description of their physical characteristics.

Meaning: 'Covered' means to be concealed or protected by something, indicating that the feet of the male penguin are shielded by a layer of skin and feathers.

Wrong options:

• powered: 'Powered' suggests being equipped with power or energy, which does not fit the context of describing the physical state of the feet.
• caved: 'Caved' implies a hollow or sunken state, which does not accurately describe the condition of the penguin's feet in this context.
• carved: 'Carved' suggests being shaped or sculpted, which does not fit the intended meaning of being enveloped or protected.