Option 1 -> "surge" means a sudden increase or forward movement, not the same as enormous.
Option 2 -> "monumental" means great in size, extent, or importance, which is synonymous with enormous.
Option 3 -> "propelling" means driving or pushing forward, not related to size or magnitude.
Option 4 -> "resilient" means able to recover or bounce back, not related to size.
Hence, Option 2: monumental -> The passage uses "monumental transformation" to describe the enormous change in India's solar installed capacity over the last five years, making it the perfect synonym for "enormous" in this context -> correct