Option 1 -> "obvious" typically describes facts or situations that are easy to understand, not physical features that stand out.
Option 2 -> "apparent" means clearly visible, but is more commonly used for things that become clear through observation rather than striking visual features.
Option 3 -> "evident" refers to something plain or clear, usually facts or truths, not distinctive physical characteristics.
Option 4 -> "conspicuous" means standing out so as to attract attention and be clearly visible.
Hence, Option 4: conspicuous -> "Conspicuous" is specifically used to describe something that is strikingly noticeable and attracts attention, making it perfect for describing distinctive red hair that caused the film star to be immediately spotted and recognized in public -> correct