Which answer matches this clue: the doubling of word-initial consonants after certain trigger words, as in a casa pronounced accasa?

• A Gorgia toscana
• B Metafonia
• C Lenizione
• D Raddoppiamento fonosintattico ✓

Raddoppiamento fonosintattico is a sandhi phenomenon unique to the language among Romance varieties; it is not represented in standard orthography.