I saw a train approaching the station. I wanted to tell my friends be ready with their bags to get into the train. I said: Train arrived be ready. Afterwards I realised that "Train arrived" is past tense which is incorrect to use in present tense. Should I have said this? Train arrives...

Recruiters prefer candidates to show a focus in their job applications. Do we need “a” here? What would change if “a” were removed? After all “focus” is both countable and uncountable noun. Some dictionaries list it as uncountable, but still use indefinite article before it: unc...