A
An arbitrary Turing machine halts after 10 steps.
B
A Turing machine prints a specific letter.
C
A Turing machine computes the product of two numbers.
Explanation
Case (a):
Just run the TM for 10 steps and see it halts or not. So this is decideable.
Case (b):
The printing problem of TMs is Undecidable. This can be reduce to the halting problem when the TM halts let it print something.
Case (c):
Multiplication, Addition can be done by TM so this is decidable.
