Eviction Reason in CT

[Robin Lee]

I am evicting a previous owner from a property that I won at a tax auction in CT. I need to choose a reason out of five, to evict someone in CT. What reason would I choose? 

Expiration of lease

Nonpayment of rent

Breach of tenant's statutory duties

Breach of lease terms

Illegal conduct or serious nuisance

Thank you for your help!

[Robin Lee]

I purchased the property at a tax auction. There was never a lease. I can not do a execution of ejectment because the case was never filed in court. I have to evict using the landlord tenant route, but I don't know which reason to choose.