Hi !!
Es dudoso que mucha gente prefiera comer mariscos.
<em>Es dudoso que + subjunctive</em>
<em>mucha gente => + verb 3rd person singular</em>
<em>-</em>
<em>☺☺☺</em>
Thta is the correct asnwer c) del
The correct word to complete the sentence is tuvieron.
Ellos tuvieron un perro blanco.
The answer to the question is Beben.
