What causes the Earth's crust to slowly move?

How am i supposed to know your lecture

Answer were lower;

Mexico has a host of environmental problems, including significant chemicalpollution  from factory discharges and waste dumping, but the main threat to itsbiodiversity  probably stems from  deforestation  and other natural habitat losses. forest habitat is lost for a number of reasons

Why you put last one a? i think is b.