题目内容：

    California’s Yosemite National Park is home to many stunning waterfalls. However, from mid-to-late February each year, the unlikely star of the preserve is Horsetail Fall-a small waterfall that forms over the eastern edge of the park’s famous vertical rock formation, El Capitan, every winter. That’s because, during the two-week-period, the temporary1,000-foot fall frequently transforms into a red “firefall” for about ten minutes a day during sunset.

For the phenomenon to occur, several conditions need to coincide. There must be enough snow and snow must be melted to form the waterfall. During drought years, Horsetail Fall is reduced to a trickle flowing slowly in drops or does not appear at all. Additionally, the skies have to be entirely clear. Even a slight mist is enough to ruin the illusion (错觉) of fire falling down the cliffs. Finally, the sun has to strike the water from the right angle to set the waterfall “burning” brightly.

The “firefall” has been popular with professional and amateur photographers since the 1940s.However, in recent years, thanks to social media, its fame has risen to new heights, with thousands of people flocking to the national park each February. In 2019, over 2,200 people crowded into the small viewing areas on February 22, the best day to see the light show last year. However, the visitors not only stepped on sensitive vegetation but also left behind large amounts of rubbish.

To prevent a repeat of the unfortunate incident, in 2020, the park service closed two of the ideal viewing areas. The only one open required a 1.5-mile-long hike. However, the 3-mile round-trip, as well as a warning by the officials that a dry spell turned the fall into a trickle, leaving the possibility of a “firefall” in doubt, didn’t not seem to have deterred fans. Hundreds of people made their way to Horsetail Fall to catch a glimpse of the light show. Hopefully, Horsetail Fall enthusiasts would be more respectful of the natural environment this time.

1.When can the “firefall” be seen?

A.About at dawn.

B.Exactly at noon.

C.Just before dusk.

D.Late at night.

2.Which of the following conditions must be met for the “firefall” to be visible?

A.The temperatures have to be warm enough.

B.Horsetail Fall must be reduced to a trickle.

C.There has to be enough slight fog in the sky.

D.The waterfall must be frozen down the cliff.

3.What do we know from Paragraph 3?

A.The “firefall” was discovered by a photographer.

B.The viewing areas were equipped with telescopes.

C.Social media offer new tools to view the “firefall”.

D.The tourists caused the environmental pollution.

4.What does the underlined word “deterred” in the last paragraph mean?

A.Disapproved. B.Discouraged.

C.Disturbed. D.Distinguished.