Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Lead poisoning in children is a major health concern. Both low and high doses of paint can have serious effects. Children exposed to high doses of lead often suffer permanent nerve damage, mental retardation, blindness, and even death. Low doses of lead can lead to mild mental retardation, short attention spans, distractibility, poor academic performance, and behavioral problems.

This is not a new concern. As early as 1904, lead poisoning in children was linked to lead– based paint. Microscopic lead particles from paint are absorbed into the bloodstream when children ingest flakes of chipped paint, plaster, or paint dust from sanding. Lead can also enter the body through household dust, nailbiting, thumb sucking, or chewing on toys and other objects painted with lead–based paint. Although American paint companies today must comply with strict regulations regarding the amount of lead used in their paint, this source of lead poisoning is still the most common and most dangerous. Children living in older, dilapidated houses are particularly at risk.

Which of the following does the passage infer?

A. Paint companies can no longer use lead in their pain

B. Paint companies must limit the amount of lead used in their paint

C. Paint companies aren't required to limit the amount of lead used in their paint

D. Paint companies have always followed restrictions regarding the amount of lead used in their paint

Trộn 100 ml dung dịch Al₂(SO₄)₃ 0,2M với 100 ml dung dịch HCl xM thu được dung dịch Y. Cho 10,96 gam Ba vào dung dịch Y, thu được 14,76 gam kết tủa. Giá trị của x là :

A. 0,30

B. 0,15

C. 0,10

D. 0,70