Questions

1. Lichens are plants that grow in exposed places such as rocks or tree bark.

2.  Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere.  

3. They need to be very good at absorbing water and nutrients to grow there.

Again, before you apply for a job to a call center you should be aware that most of the call centers cater to English speaking customers and this needs you to speak clear English without any grammatical mistakes.