2 moles of iso-pentylene on reaction with compound A gives compound B, which on treatment with 1-phenyl-2-butyne followed by oxidation with H2O2 and NaOH results in the compound C. A is in turn generated by treating BCl3, with LiAlH4. The compound C gives:
Iodoform test
4BCl3+3LiAlH4⟶2B2H6+3LiAlCl4
So we have a dialkylborane where there is just the one hydrogen atom bonded to the boron atom for reduction. Plus, the alkyl group - the substituent attached to the boron is a bulky one. When this dialkylborane is made to react with 1-phenylbut-2-ene, the hydrogen attaches itself with the carbon 3 from the methyl group because there is a bulky alkyl group present in the reducing agent (dialkylborane).
C is a methyl ketone, which means, it will give a positive haloform test!