单项选择题

TEXT C
I find it easiest to look forward by looking back to the "Great Labor Migration" of 1948-55, seen at the time as a matter of black guests coming to a white host. It’s a quasi-imperial perception that has shifted since the 1970s, but the social problems and deficiencies it engendered dog us still^①.
It’s highly questionable whether Britain is an open society even now. Against the upward trend in the 1980s of ethnic minorities breaking into the professions and the media must be set objective evidence of a very racist society. Since the Stephen Lawrence affair the government has at least been talking about the existence of racism, but it’s always the case that racism diminished in times of prosperity. When the economic going gets tough, people want someone to take their feelings out on.
The social landscape seems to me at a surreal crossroads. Britain fosters images of itself as homogenous, to be white is no longer the central defining feature, but there remain various kinds of "Britishness". So I can envisage the future in two very different ways.
The first is broadly the way Britain is at the moment: a mosaic of communities: Bangladeshi, Afro-Caribbean, Chinese or Jewish holding fast to a strong social identity, but lumbered also with a whole raft of benefits and disadvantages, most of them defined in economic terms. It’s possible that will still be the pat tern in 50 years time, but not very likely. Instead, I expected the old duality of a "host community" and "immigrants" whose bad luck it is to be excluded and disadvantaged to have vanished. Some ethnic communities may make a point of survival, but only those who are most proud of their cultural roots.
The alternative is a pick-and-mix social landscape. At the moment ethnic minorities are moving in different directions at different rates, with personal and social engagement across ethnic boundaries increasing all the time. One crude indicator is the level of mix-race marriage: one in five Bangladeshi and Pakistani men born in Britain now has a white with, and one in five babies born in Britain has one Afro-Caribbean and one white parent.
This implies a Britain in which people will construct multiple identities defined by all sorts of factors: class, ethnicity, gender, religion, profession, culture and economic position. It won’t be clear-cut. Not all ethnic, minorities, or members of an ethnic minority, will be moving in the same direction of identifying the same issues at the heart of their identities. It’s about deciding who you are, but also about how other people define you.
That’s what will be at the heart of the next 50 years: enduring communities linked by blood through time versus flexible, constantly shifting identities. Identity won’t be about where you have come from; it will be a set of values you can take anywhere that is compatible with full participation in whichever society you live in^②.
What is the main subject of the passage