When can I omit the subject?

Question

Can I omit the subject if it has been mentioned in a preceding sentence? For example, is the phrase inside the parentheses necessary in the below?: >> The sculpture A exhibits degradation at a seemingly increased rate from 30 years ago. However, the surrounding environment is considered not to have changed at a significant level since (the sculpture was) carved.

Answer 1

No. You'll then have a sentence that, strictly speaking, conveys that the surrounding environment was carved. The reason is that "since the sculpture was carved" is an adverbial dependent clause with subject (sculpture) and verb (was carved). You can't just omit parts of dependent clauses.