The best combination for key earthen structures which

It's a piece of __________.

Directions: Below given sentences contain two blanks. Fill in the blanks with appropriate words. 

The yield has gone up …… this year while prices have fallen by half,……….. heavy losses to the chilli growers.

Choose the option that provides the most appropriate and contextually fitting word for each blank.

This structure is easier to ________ from radio maps of either neutral hydrogen or molecular clouds, since both can be detected through the dust.

The building that we came across while travelling today was ___________.