Hi, YSchneider . I am not a native speaker and this is indeed a tough grammar point for non-native speakers. Here is an extract from CGEL*: Did you lock the front door?
ESL General English Grammar Questions
by
Diamondrg
116 days ago
Simple Present, Grammar, Verbs, Difference Between, Constructions, Tenses, Adverbs, Stative Verbs, Simple Past, Present Perfect, Past Tenses