Option 1 -> "Alternatively or" suggests choices rather than showing the contrasting behavior of desert flowers.
Option 2 -> "Consequently and" implies cause-effect, but appearing isn't a consequence of being invisible.
Option 3 -> "Nevertheless, so" combines contrast with result illogically - these conjunctions work against each other.
Option 4 -> "Actually, but" properly shows the contrast between prolonged invisibility and sudden appearance, with "actually" emphasizing the surprising nature of this contrast.
Hence, Option 4: actually, but -> The sentence describes two contrasting states of desert flowers: long-term invisibility versus sudden appearance. "But" is the appropriate conjunction to show this contrast, while "actually" adds emphasis to highlight the surprising nature of their sudden emergence after years of dormancy -> correct