This question requires us to fill in the blanks in a given passage to make it coherent and grammatically correct. We need to select the most appropriate word from the options provided for each blank. We are specifically asked to focus on blank number 4.

Let's look at the passage with the blanks:

An appetising and nutritious meal is always recommended because what we eat (1) ____ our senses. The effect of food on our mind, body and spirit had been the centre (2) _____ discussion even in ancient Greece, when Pythagoras argued in favour of a healthy, vegetarian (3) ______. Though at the time when the philosopher lived, in around 500 BC, the term 'vegetarianism' was (4) _____, his diet came to be known as 'the Pythagorean diet'. He is known for his theory on geometry, but few are aware of his profound (5) ______ on food habits!

Analyzing the Blank No. 4

The sentence containing blank 4 is: "Though at the time when the philosopher lived, in around 500 BC, the term 'vegetarianism' was (4) _____, his diet came to be known as 'the Pythagorean diet'."

This sentence contrasts the lack of a specific term ('vegetarianism') at the time Pythagoras lived (around 500 BC) with the fact that his diet, which we would now call vegetarian, was known by a different name ('the Pythagorean diet'). The word for blank 4 should indicate that the term 'vegetarianism' was not in use or not recognized at that historical period.

Let's examine the options for blank 4:

• Option 1: knowing - This is the present participle of 'know' and is usually used to describe someone who possesses knowledge (e.g., 'a knowing glance') or the act of acquiring knowledge. It doesn't fit grammatically or contextually to describe a term.
• Option 2: unknown - This adjective means 'not known or familiar'. If the term 'vegetarianism' was unknown in 500 BC, it fits the context perfectly, explaining why his diet was called something else ('the Pythagorean diet').
• Option 3: knowledgeable - This adjective describes a person who possesses a lot of knowledge. It cannot be used to describe a term.
• Option 4: known - This is the past participle of 'know' and means 'recognized, familiar, or within the scope of knowledge'. If the term 'vegetarianism' was 'known' in 500 BC, the sentence structure "Though... his diet came to be known as 'the Pythagorean diet'" wouldn't make sense, as it implies a contrast where the term wasn't the common name.

Based on the analysis, the word that best fits the context of the sentence and the overall meaning of the passage is 'unknown'. It clearly indicates that the specific term 'vegetarianism' had not been coined or was not in common use during Pythagoras's time.

Revision Table: Completing the Passage Blanks

While we focused on blank 4, let's consider what words would likely fill the other blanks to complete the passage meaningfully. This helps understand the context around blank 4.

Additional Information: Pythagoras and Diet

Pythagoras, a Greek philosopher and mathematician from around 500 BC, is famous for the Pythagorean theorem. However, his school of thought, Pythagoreanism, also advocated for a specific lifestyle which included dietary practices. While the modern term 'vegetarianism' didn't exist then, the Pythagorean diet was largely plant-based, excluding meat and sometimes other animal products like beans. This adherence to a meat-free diet was often linked to philosophical and ethical beliefs, including the idea of transmigration of souls, which suggested that animals might house human souls, making meat consumption problematic.

The passage highlights that although the term 'vegetarianism' was unknown in his time, the practice of following a diet similar to what we now call vegetarian existed and was associated with his name. The development of specific terms like 'vegetarianism' came much later, with the word itself appearing in the English language in the mid-19th century.