To write an Exclusion Script to exclude sending an email at send time when comparing against a Boolean field in the Sendable Data Extension, the developer can use:
* %%SendBoo1 < 1 (B) - This script directly checks if the Boolean field SendBoo1 is less than 1, effectively excluding records where the field is false.
* %%=Lookup('Excluded', 'SendBoo1', 'Subscribekey', _Subscribekey) == false (C) - This script performs a lookup to check the value of SendBoo1 in the 'Excluded' data extension, comparing it against the Subscribekey. If the value is false, the email is excluded.
References:
AMPscript Guide
Salesforce Marketing Cloud Documentation