A. It is usually a good idea to use your equity line of credit as your cash reserve, if you understand the potential risks.
First, the advantages - equity line of credit is a mortgage loan with your house as the collateral, because it has a collateral, its interest rates are typically a lot lower than credit card debts which credit companies have no collateral from you. Even better, with equity line of credit, if you don't use it, it carriers no interest charge (some banks might charge you an inactivation fee).
Now, the potential risk - a bank could cancel your equity line of credit at any time. Unfortunately this could happen at the time you need access to the money the most - when you lose a job. Worse, if your house value also drops while you lost your job (millions of Americans had this experience during the 2008 financial crisis), or the banks find out you are unemployed, they may cancel your equity line of credit account.
If you understand this worst case scenario and be prepared for it, then it's a good idea not to put lots of rainy day funds in a bank account earning nothing, an equity line of credit is a great alternative.