The only important historical solar system object which has not yet been visited up close by satellite spacecraft is..
A) a comet or asteroid
b) pluto
c) neptune
d) saturn's moon titan
I don't know of any comets or asteroids which have had satellite spacecraft orbit them. Frankly, considering the masses of those, it would be quite a fete.
thank you
Comets have been impacted by spacecraft, and the "tail" of Halley was sampled. At least asteroid have been photographed "up close", and so was Neptune, by Voyager 2. The answer to your question is Pluto.
See http://www.bobthealien.co.uk/spacecraft.htm
for a detailed list of solar system probes
Assuming that a spacecraft lands on an asteroid and bores a hole perpendicular to its surface; it is noticed that the sun shines straight down to the bottom of the hole. Another hole is bored 10 miles "north' of the first hole at the same time, but it is noticed that the Sun makes a 20 degree angle to rod placed into that hole - what is the circumference and radius of that asteriod?
The correct answer is (A) a comet or asteroid.
Comets and asteroids are small celestial bodies that orbit the Sun, and they have been studied remotely through telescopes and ground-based observations. However, as of now, no satellite spacecraft has been sent to visit a comet or asteroid up close.
To reach this answer, you can eliminate the other options by checking the historical records of satellite spacecraft missions.
B) Pluto: In 2015, NASA's New Horizons probe flew by Pluto and provided us with close-up images and valuable scientific data about this distant dwarf planet.
C) Neptune: NASA's Voyager 2 spacecraft visited Neptune in 1989 and obtained detailed data and images of this gas giant and its moons.
D) Saturn's moon Titan: The Cassini-Huygens mission, a joint effort by NASA and the European Space Agency (ESA), included a probe called Huygens that successfully landed on Titan in 2005. Data and close-up images were sent back to Earth, providing significant insights into the moon's surface and atmosphere.
Therefore, the only option remaining is (A) a comet or asteroid, making it the correct answer.