The question asks to identify the archaeological site where a distinct Harappan script inscription, characterized by its large alphabet size, was discovered.

Dholavira: Site of Large Harappan Script Inscription

Among the listed sites, Dholavira is renowned for a significant finding related to the Harappan script.

Key Discovery at Dholavira

• Archaeological excavations at Dholavira, located in Gujarat, unearthed a large stone slab.
• This slab contained an inscription composed of multiple large-sized symbols of the Indus script.
• This discovery is often referred to as a 'signboard' and is notable for the sheer size of its alphabets, which are considerably larger than typical Harappan script findings elsewhere.

Reasoning

The defining characteristic mentioned in the question – "huge alphabets" – directly corresponds to the unique inscription found at Dholavira. While other sites like Mohenjodaro and Kalibangan have yielded Harappan script inscriptions, they are generally not associated with alphabets of such monumental size as found at Dholavira.