Ten thousand I saw at a glance' is an example of -

• 'Ten thousand I saw at a glance' is an example of - Hyperbole.

• An exaggerated statement or an extreme overstatement is termed as - Hyperbole.
- Hyperbole - অতিরঞ্জন বা অতিশয়োক্তি।
- কোন ব্যক্তি বা বস্তুকে তার বাস্তব অবস্থানের চেয়ে বাড়িয়ে বলা।
যেমন - 
- I am so hungry that I could eat a horse.
- He said to his beloved, 'I will cry a river for you.'

• অন্যদিকে, প্রশ্নে উল্লেখিত অপশন গুলোর মধ্যে - 
• Irony - A statement or a situation or an action which actually means the opposite of its surface meaning.
• Alliteration - The repetition of an initial consonant sound is called Alliteration.
• A metaphor is a figure of speech that is used to make a comparison between two things that aren't alike but do have something in common.

Source: An ABC of English Literature by Dr. M Mofizar Rahman