I wrote this with no "a" before "andar". What is the rule for when you need the "a" with an infinitive and when you don't?
We use começar a + infinitive to say you will start an action.
To describe routine or steps you can use começar + gerund (começo meu dia comendo uma maçã)
Why is "caminhar" not accepted? Doesn't it mean "to walk" the same as "andar"?
It should be accepted also.