题目内容：

Can people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes．Scientists have found the gene that determines skin colour．

  The gene comes in two versions, one of which is found in 99 per cent of Europeans．The other is found in 93 to 100 per cent of Africans, researchers at Pennsylvania State University report in the latest issue of Science．

    Scientists have changed the colour of a dark-striped zebrafish to uniform gold by inserting a version of the pigment(色素) gene into a young fish．As with humans, zebrafish skin colour is determined by pigment cells, which contain melanosomes(黑色素)．The number, size and darkness of melanosomes per pigment cell determines skin colour．

    It appears that, like the golden zebrafish, light-skinned Europeans also have a mutation(变异) in the gene for melanosome production．This results in less pigmented skin．

  However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebrafish genes．

  Humans acquired dark skin in Africa about 1．5 million years ago to protect bodies from ultra-violet rays(紫外线) of the sun, which can cause skin cancer．

But when modern humans leave Africa to live in northern latitudes, they need more sunlight on their skin to produce vitamin D．So the related gene changes, according to Cheng．

  Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin colour, said Cheng．

    The new discovery could lead to medical treatments for skin cancer．It also could lead to research into ways to change skin colour without damaging it like chemical treatment did on Michael Jackson．

1.What is the main idea of the passage?

A． People can’t change their skin colour without any pain．

B． The new discovery helped find ways to change skin colour safely．

C． Pop king Michael Jackson often changed his skin colour as he liked．

D． Scientists have found out that people’s skin colour is determined by the gene．

2.It can be inferred from the passage that ________．

A． nowadays changing the skin colour with the chemical treatment has bad effect

B． Europeans and Africans have the same genes

C． the new discovery could help to find medical treatments for skin cancer

D． there are two kinds of skin genes

3.Scientists have done an experiment on a dark-striped zebra fish in order to ________．

A． find the different genes of humans

B． prove the humans’ skin colour is determined by the pigment gene

C． find out the reason why the Africans’ skin colour is dark

D． find out the ways of changing people’s skin colour

4.Which of the following statements is TRUE?

A． Michael Jackson died of skin damage caused by chemical treatment．

B． American blacks produce more vitamin D with their skin than others．

C． The gene determining skin colour exists widely in whites, blacks and Asians．

D． The melanosomes in the skin of blacks usually cause skin cancer more often．