Based on ur statements, isn't Bank B is conlanfirm offering u best rate at 3.0%? Why still wait A that can only offer 3.05% or C that say around 3%?
Anyhow... U can verbally 'accept' and only officially go sign the best one after your quarantine, no need feel bad as this is a normal consumer market/attitude.
I say this coz i does similar work, used to be rejected later despite client earlier on agreed.