“Two turtles were slowly crossing the dusty road when we passed by.” The verbal tense in the passage were slowly crossing is Past progressive tense.

Sim, o tempo verbal na frase "Two turtles were slowly crossing the dusty road when we passed by" é o passado progressivo (past progressive tense). Nesse tempo verbal, usamos o verbo "to be" no passado (were) seguido do verbo principal no gerúndio (crossing). Ele é usado para descrever uma ação contínua que estava ocorrendo no passado.