题目内容：

    Using natural and organic products for skincare is increasingly popular-and that includes suncream. Many websites, including Pinterest and Instagram, feature users' recipes for homemade suncream. Judging from the comment, the rise in interest for homemade suncream is because some people fear the chemicals in shop-bought suncream and believe that natural products mixed at home will be better at protecting them from the sun's harmful rays. The fear originates from recent news that some suncream elements seem to disturb hormones (荷尔蒙).

Many of the homemade suncream recipes contain elements like shea butter and cocoa butter as well as coconut and vitamin E oils. The sun protection factor (SPF) values for these elements, according to the authors of these recipes, are between four and six. These SPF values, if true, are not enough to protect the skin against the harmful effects of sunlight. Some recipes include carrot seed essential oil, which the authors claim to have an SPF of 35-40. But this is unlikely, given the small amount used in these recipes. The European Commission recommended SPF factor for moderate skin protection is 15-29 (and 30-50+ for high protection).

The sun's most harmful rays are ultraviolet (UV) radiation-notably UVB and UVA radiation. UVB has a shorter wavelength and doesn't go far into the skin, but it is very dangerous as it can change the DNA in skin cells and cause skin cancer. UVA has a longer wave- length and can go much deeper into the skin. UVA can cause harmful reactive oxygen molecules (分子)called “free radicals” to form. These molecules can damage fat, protein and DNA in the skin, thereby weakening the normal function of skin cells.

Shop-bought suncream contains approved UV-blocking molecules that block UVA and UVB rays. Zinc oxide (氧化锌)is one of these UV-blocking materials. It has been extensively tested to determine the most effective size for blocking harmful rays. It is not clear whether the zinc oxide powder recommended for the homemade recipes meets with the recommended size or proportion needed.

1.What may concern consumers of the shop-bought suncream?

A.The price of it. B.The hormones in it.

C.The chemicals in it. D.The production process of it.

2.What are SPF values used for?

A.Measuring the amount of chemicals in suncream.

B.Measuring the harm suncream do to people.

C.Measuring the hormone level of suncream.

D.Measuring the protective effect of suncream.

3.What does paragraph 3 mainly talk about?

A.How sun protection products work.

B.What harm the sun's rays bring to skin.

C.How the sun's most harmful rays form.

D.How UVB and UVA radiation can be blocked.

4.What can be inferred from the last paragraph?

A.Shop-bought suncream needs more tests.

B.More zinc oxide powder is beneficial to skin.

C.Shop-bought suncream is more suitable for people.

D.More chemicals will be added into shop-bought suncream.