Question

Fill in the blank with the correct form of the verb Haber. Cuando iba al supermer “El Rancho”, siempre_mucha gente esperando para comprar carne. Había, habían, hay, hubo.

Answer 1

The answer is “había” because he’s talking in the past

Answer 2

The correct answer is había.
The verb HABER in Spanish is used to denote meanings such as "There is" or in the past "There was" something. Here, the sentence means - When I went to the "El Rancho" supermarket, there were always a lot of people waiting to buy meat. 
When used with this meaning, the verb HABER has only two forms - HAY for present and HABIA for past. Habian and hubo are incorrect forms.