Fill in the blanks with appropriate similes or adjectives from the brackets.
With technology at our fingertips, it is now as ….. (a) ….. (easy, complex, tough) as abc to scan across the world and explore the unexplored. The boundaries that are as thick as ….. (b) ….. (brick, iron, glass) crumble down to help us experience a unified existence. Now, man is as busy as a ….. (c) ….. (snail, bee, sloth), joyously defeating the conventions and customs of yesteryears. His vision is as ….. (d) ….. (clear, vague, dim) as crystal and his attitude is as stubborn as that of a mule.