二、簡答題
41. What chemical bond results in the cohesion between water molecules?

5. As shown in Figure 4, in cross section, a cylindrical capacitor of length L formed by two coaxial cylinders of radii a and b. Assuming L is much greater than b so that we can neglect the fringing of the electric field that occurs at the ends of the cylinders. The capacitor is charged in a circuit, and the electric potential difference between the two cylinders is V. The capacitor is then disconnected from the circuit. A liquid dielectric material of dielectric constant k is injected to the capacitor, and is only half filled. After filling the dielectric material, what is the electric potential difference between the two cylinders? 

6. A copper rod of mass m rests on two horizontal rails with a distance d apart from each other and carries a current i from one rail to the other as shown in Figure 5. The coefficient of static friction between rod and rails is u. A uniform magnetic field B is applied to the system and puts the rod on the verge of sliding, what is the angle of magnetic field with respect to the direction of tails, if the applied magnetic field is at minimum? 

7. Consider a "four-slit" interference experiment as shown in Figure 6. The distance between the slits is d, while the distance between the slits and the screen is D (D＞＞d). A coherent monochromatic light at a wavelength of λ is directed to the slits. Find the distance between the first dark fringe and the central maximum on the screen. 

8. A relativistic particle of mass M with total energy E decays into a lighter particle of mass m together with some other undetected particles. The particle m also decays afterwards. The proper lifetime of particle M is measured to be T and the proper lifetime of particle m is t. If half of the kinetic energy of particle M has been transmitted to particle m during this process, what are the flight distances of the particle M and of the particle m, from an observer at rest? 

42. What is the driving force for water movement within the plants?

43. What vascular tissues or cells contain this H³/sucrose symporter?

44. Which photosystem is responsible for water splitting?

 (1) What is the "species richness" in these two communities?

(2) Which community has a higher level of diversity?

46. What is the evolved biological function of the CRISPR/Cas system in bacteria? How does the CRISPR/Cas system work in gene editing?