Rule reminder
Common B2 error: using 'perché' + subjunctive when you mean CAUSE (should be indicative), or using 'perché' + indicative when you mean PURPOSE (should be subjunctive). Remember: CAUSE = perché + indicative; PURPOSE = perché + subjunctive (= affinché). Also: 'non perché' + subjunctive = 'not because' (denial of cause), whereas 'non perché' + indicative = 'not because' (factual denial).
'Gli ho dato le chiavi perché possa entrare.' Is this sentence correct? What does it mean?