Word patterns B2 (work)
to be an expert in a particular part of a subject or profession (2 phrases)
specialise in smth / specialise in doing smth
practise a lot, learn the skills that you need to do your job or something else
train to do smth
If you're ... ... it is your job or duty to deal with it and make decisions relating to it (2 phrases)
responsible for smth / responsible for doing smth