Sea-level changes along a coastline may be caused by

1. melting or growth of polar ice caps

2. tectonic uplift

3. all of these

4. tectonic subsidence

3. all of these

Explanation:

Sea level can be changed by the following factors -

Tectonic uplift of the ocean basin will increase the sea level while the tectonic uplift of the coastal region will reduce the sea level .

Hence this option is correct .

Melting of polar ice caps will leads to rise in sea level while growth will reduce the sea level along the coastline,

Hence this option is correct .

Tectonic subsidence also changes the sea level along the coastline so this option is also correct.

Therefore ,  The correct answer is ( 3 ) .  

a is the answer i believe.