If it is for clearing job exams, then you are good to go with Wren and Martin. Though I am not sure what kind of questions are asked there. But from my very brief experience on some websites that deal with job exams it seems that school level grammar is asked there and similar answers that are considered correct in school os expected.
I think I also read Wren and Martin back in school but I simply can't remember because my subject was not English. And I read grammar in very elementary level, in my initial days of school days.
Hello! When you call someone to learn a bit about what's new with them and such, do you think of that as keeping in touch, getting in touch or touching base, over the phone? If I'm trying to express that to the person I'm calling and I say something like "Just calling to..." would either sound as natural to you in that context? Do you think of those as the same kind of "touch(ing)" so to speak?