Secondary Index is created on key field, which is dense index.
Since we have 16384 records in data file, index is created for every entry in 1st level index file.
In 1st level index file size of each record is 10+6 = 16B
1st level index contains 16384 records
No of records/block in 1st level index = 1024/16 = 64 records
No of blocks in 1st level index = 16384/64= 256
Now, we have another 2nd level index which contains 256 records(1 record for each block in 1st level index)
No of blocks in 2nd level index= 256/64= 4
Hence option c) is correct