A good answer might be:

Because floating point zero has the same representation as integer zero, 32 zero-bits.

Double Precision

MIPS also has hardware for double precision (64 bit) floating point operations. For this, it uses pairs of single precision registers to hold operands. There are 16 pairs, named $f0, $f2, — $f30. Only the even numbered register is specified in a double precision instruction; the odd numbered register of the pair is included automatically.

Some MIPS processors allow only even-numbered registers ($f0, $f2,...) for single precision instructions. However SPIM allows all 32 registers in single precision instructions. These notes follow that usage.

QUESTION 3:

Remember the load delay, where it takes an extra machine cycle after a load instruction before integer data reaches a general purpose register? Do you think there is a load delay for floating point load operations?