S1: Doubling the line size halves the number of tags in the cache.
If we double the line size, then the number of lines in a block will decrease (exactly half, assuming the cache size remains constant), as number of lines get halved the number of tags will also get halved.
S2 : Doubling the (set) associativity increases the number of tags in the cache.
If we double the set associativity, the number of sets will decrease, hence the bits required for number of bits will decrease, block offset remains the same, so tag bits will increase but number of tags remains same.
Doubling the line size usually reduce compulsory misses.
The more number of lines in a cache, the more the compulsory misses. Doubling line size will half the number of lines, so cumpulsory misses decrease.
S1 & S3 should be correct.