I wonder if someone could tell me which one of the following choice fits the best for my example?
……………..the World Heritage Organization has protected hundreds of sites ranging from beautiful natural islands to buildings in large cities to ancient ruins.
a) up to now
b) so far
d) by now
e) until now
For me, they all work and they all mean the same in this specific context. But I wonder if someone do me a favor and let me know if here is any slight nuance or usage feature for each one over the others. For example I am guessing there should be a difference in politeness or formality degree between them.
All opinions are welcome.