I have a question regarding your last statement. Here 'regarding' is a/an -

Regarding (preposition):
English Meaning - In relation to; about.
Bangla Meaning - সম্পর্কে; বিষয়ে।

I have a question regarding your last statement.- এখানে 'regarding' হচ্ছে Participle preposition.

Participle preposition:
- কতগুলো Present participle এবং past participle- preposition এর মত ব্যবহৃত হয়ে থাকে, এদের Participle preposition বলে।
- যেমন: Regarding this matter I know nothing.

Source: A Passage to the English Language by S.M. Zakir Hussain.