1. Comparative structure: "Conversely, offline learning requires students to be physically present at specific times and locations, which can restrict flexibility and increase time spent commuting." This sentence effectively uses a comparative structure to highlight the differences between online and offline learning.
2. Adverbial clauses of time: "at any time" and "at specific times" serve as adverbial clauses that specify the conditions under which learning takes place, adding depth to the description of each learning mode.
3. Passive voice: "Learners have the freedom to access educational materials" uses the passive voice to emphasize the action and the flexibility it provides, rather than the actor, which is a common and effective technique in formal writing.