[填句补文]Mexico‘s current lack of funds is also partly due to oil. The country has rich oil fields and a few years ago， when oil was expensive， Mexico was selling large quantities of oil to the USA and earning a lot of money. ________. However， the price of oil then dropped， and Mexico has been left owing enormous sums of money and with not enough income from oil sales to pay back the loans.
A.But those ruins are in danger of being seriously damaged by pollution.
B.Scientists estimate that about one millimeter of stone is worn away every twelve years.
C.At others the painted surfaces inside temples are lifting and flaking off and the stone is being eaten away.
D.The government was therefore able to borrow huge sums of money from banks around the world， thinking they would have no problem repaying their debts.
[填句补文]As part of their study， the researchers used a special machine to take action photos of the students‘ brains. ________. This is the same part of the brain that becomes active when good readers read. This activated brain area appears to include a structure that helps people recognize familiar written words quickly.
A.Do you have difficulty reading in class?
B.The pictures showed an increase in activity in the back of the brain on the left side.
C.As part of the study， 37 struggling readers received special tutoring.
D.By the end of the school year， these children could read faster than before.