Which verb tense always uses had as a helping verb

Aspot in middle of the retina that only contains cones is called the

How do cheetah kitten silver manes them to survive? quote evidence from the teaxt to support your response and explain your answer completely

What is the best way to manage oil transport on waterways? a. prevent oil spills and regulate the amount of oil that can be shipped at one time.b. use a skimmer, containment boom or chemical dispersant to clean up spilled oil.c. burn off oil spills from the water's surface when they occur.