To solve this problem, we need to determine the length of the recognition sequence for the restriction enzyme Hind II.$\newline$Restriction enzymes are proteins that cut DNA at specific sequences known as recognition sequences.$\newline$Each restriction enzyme has a unique recognition sequence, which is typically a specific number of base pairs (bp) long.$\newline$Let's analyze the options provided:$\newline \bullet$Option 1: 4 bp$\newline \bullet$Option 2: 10 bp$\newline \bullet$Option 3: 8 bp$\newline \bullet$Option 4: 6 bp$\newline$Hind II is known to have a recognition sequence that is 6 base pairs long.$\newline$This is a well-documented characteristic of Hind II, which specifically recognizes and cuts at a 6 bp sequence.$\newline$Therefore, the correct option is Option 4: 6 bp.