Answer:
C. increase because of conservation of angular momentum.
Explanation:
We know that if there is no any external torque on the system then the angular momentum of the system will be conserved.
Angular momentum L
L = I ω
I=Mass moment of inertia , ω=Angular speed
If angular momentum is conserved
I₁ω₁ = I₂ω₂
If people migrates towards Earth's equator then mass moment of inertia will increases.
I₂ > I₁
Then we can say that ω₁ > ω₂ ( angular momentum is conserve)
We know that time period T given as
[tex]T=\dfrac{2\pi}{\omega}[/tex]
[tex]T_1=\dfrac{2\pi}{\omega_1}[/tex]
[tex]T_2=\dfrac{2\pi}{\omega_2}[/tex]
If ω₂ decrease then T₂ will increase .It means that length of the day will increase.
Therefore answer is C.