Which is your favourite topic in maths?
Mine is Calculus (and Differential Equations).
C1-4 would be the easy answer but incomprehensible outside the UK . It's done at A level and does a bit of everything really but no stats which I despise
From the US system I'd pick a ghastly amalgamation of pre-calculus and trig
I liked advanced linear algebra a lot (even though I don't think it's easy), analysis caught me in its difficulty and beauty and somehow even if I haven't studied anything further yet geometry/topology keeps me interested.