Answer 2:
Jupiter exerts the largest force on Earth.
In order to get a clear idea of this answer, it will be good for you to learn about some concepts like "The gravitational attraction (F)" between any two objects, which can be determined using Newton's Law of Gravitation:
F = G * m_{1}*m_{2}/r^{2} where G = 6.674*10^{11} m^{3}/kgs^{2} is the gravitational constant, m_{1} and m_{2} and are the masses of the objects, and r is the distance between the objects (and that distance is squared in the equation).
The masses of the planets are readily found (e.g., from NASA's fact sheet), and the current distances of each planet from Earth can be found here. (Note that in NASA's fact sheet the distances are from Sun, not from Earth).
I suspect the quantity actually wanted here is the acceleration due to gravity from these other planets on an object on Earth. This is given by the above law and another of Newton's Law, F = m*a > a = F/m.
That is, to find the gravitational acceleration of each of the planets at the surface of Earth, we divide the above gravitational forces (F) by the mass of Earth (neglecting the relatively small change in r due to being on the surface of Earth instead of at the center). In this case, the value for Earth can also be calculated, using a radius of Earth of 6350 km. This is included as the last row in the following table.
Note that the units in the far left column are adjusted to make the numbers reasonable  for example, distances are in 10_{6} km, meaning millions of km, and acceleration at Earth's surface is in 10_{10} m/s_{2}, meaning the numbers (except Earth's) should be divided by 10,000,000,000.
Bringing in the relevant data and entering it into the formulae described above (use m_{1} = mass of Earth)
Planet 
Mercury 
Venus 
Earth 
Mars 
Jupiter 
Saturn 
Uranus 
Neptune 
Mass (10^{24} kg) 
0.330 
4.87 
5.97 
0.642 
1898 
568 
86.8 
102 
Distance (10^{6} km)  160.805 
93.128 
N/A 
213.675 
786.431 
1531.797 
3103.570 
4611.302 
Gravitational force F (10^{15} kgm/s^{2}) 
5.085 
223.732 
N/A 
5.603 
1222.744 
96.451 
3.591 
1.911 
Accel. @ Earth surface (10^{10} m/s^{2}) 
8.517 
374.761 
9.88 m/s 
9.385 
2048.147 
161.559 
6.014 
3.201 
From this, one can see that Jupiter exerts the largest force on Earth. This is because Jupiter has such a large mass. Venus is not that much lower despite a much lower mass, because theEarthVenus distance is far lower than the EarthJupiter distance. Similarly, the acceleration due to gravity of each of these planets on objects on the surface of Earth is largest for Jupiter. However, that acceleration (2048 * 10^{10} m/s^{2}) is ~50 million times lower than that of Earth.
See here on ScienceLine for a related question. The pages here and here are good reads to learn how the Moon and other planets affect your weight on Earth.
