A fairly straight forward calculation, but care needs to be taken to draw the diagram correctly and making sure you do the math correctly.

A.   4 C (graphite) + 5 H₂ (gas) --> CH₃CH₂CH₂CH₃ (gas)

B.   (CH₃)₃CH (gas) + 13/2 O₂ (gas) -->   4 CO₂ (gas) +  5 H₂O (gas)

C.

D.    The calculation is shown on the figure above.  The steps are :

(i)   calculate the number of moles of 2-methylpropane in 6.37g
(ii)  calculate the ΔH_c / mol for 2-methylpropane by dividing the heat given by part (i)
(iii) calculate the ΔH_c / mol for butane by recognising that ΔH_f + ΔH_c must be the same for the two isomers.