Fill in the Blanks: The ancient Egyptians believed ______ so that when these objects were magically reanimated through the correct rituals, they would be able to functions effectively.

Options a), b) and d) are grammatically incorrect. 

Option A - In the sentence, "that it was essential that things they portrayed" ,definite article (the) should be used in front of the noun(things).

Option B- This sentence implies that having every relevant detail shown as clearly as possible is important for the things that Egyptians portray. However, having every detail shown was important for the effective functioning of the things Egyptians portray. Hence this is grammatically incorrect.

Option D - Consider the phrase "that when they portrayed things, it should have". The correct phrasing would be "that when they portrayed things, they should have" or "that when they portrayed a thing, it should have". There is a singular plural mismatch occurring here. Hence this option is incorrect as well.

The correct sentence is "The ancient Egyptians believed it was essential that the things they portrayed had every relevant feature shown as clearly as possible, so that when these objects were magically reanimated through the correct rituals, they would be able to functions effectively."