Rules glossary
↑ Parent rule: 700.2 A spell or ability is modal if it has two or more options in…
700.2c If a spell or ability targets one or more targets only if a particular mode is chosen for it, its controller will need to choose those targets only if they chose that mode. Otherwise, the spell or ability is treated as though it did not have those targets. (See rule 601.2c.)
No sub-rules.