Option 1 -> intrusive means imposing or intruding; similar to obtrusive as both suggest something that stands out or pushes itself forward.
Option 2 -> subtle means delicate or understated; opposite meaning to obtrusive.
Option 3 -> transient means temporary or fleeting; unrelated to the concept of being noticeable or prominent.
Option 4 -> distinguished means notable or eminent in a positive way; suggests standing out but with positive connotation unlike obtrusive.
Hence, Option 1: intrusive -> is the closest synonym to obtrusive as both words convey the idea of something that imposes itself noticeably (though it should be noted that in the sentence context describing seamless blending, neither word fits logically) -> correct