If you must, travel by plane. If you can avoid it, try a train instead.

A. You will support local community if you stay in locally owned accommodation and buy products from local people.

B. You will support local community unless you stay in locally owned accommodation and buy products from local people.

C. You stay in locally owned accommodation and buy products from local people because you will support local community.

D. You stay in locally owned accommodation and buy products from local people only if you will support local community.

A. You don't have to educate yourself about the destination you are visiting by reading guidebooks and travel articles.

B. You aren't required to educate yourself about the destination you are visiting by reading guidebooks and travel articles.

C. You should educate yourself about the destination you are visiting by reading guidebooks and travel articles.

D. You may object to educating yourself about the destination you are visiting by reading guidebooks and travel articles.

A. You should try to limit the use of natural resources unless they are running out in many tourist destinations.

B. Because you try to limit the use of natural resources, they are running out in many tourist destinations.

C. You should try to limit the use of natural resources, so they are running out in many tourist destinations.

D. Natural resources are running out in many tourist destinations, so you should try to limit their use.

A. We don't allow the local people to hunt endangered species for our consumption, so they will become extinct sooner.

B. If we allowed the local people to hunt endangered species for our consumption, they would become extinct sooner.

C. We don't allow the local people to hunt endangered species for our consumption unless they will become extinct sooner.

D. They will become extinct sooner if we don't allow the local people to hunt endangered species for our consumption.

A. You can't remove any products from the nature, so it is illegal.

B. Because you can't remove any products from the nature, it is illegal.

C. You can't remove any products from the nature because it is illegal.

D. You can't remove any products from the nature unless it is illegal.

A. Living areas are damaged or destroyed because they might not be available to future generations.

B. Living areas are damaged or destroyed, but they might be available to future destroyed.

C. Living areas might not be available to future generations if they are damaged or destroyed.

D. Living areas might not be available to future generations unless they are damaged or destroyed.

A. Tourists are free to learn about the vital eco-systems before arriving.

B. It is optional for tourists to learn about the vital eco-systems before arriving.

C. Tourists are not required to learn about the vital eco-systems before arriving.

D. Tourists are required to learn about the vital eco-systems before arriving.