What does our most recent common ancestor with the lungfish look like?

Tetrapods

Explanation:

Tetrapods are the most recent common ancestor with the lungfish look like.

Ancient species of lung fish are the ancestors of tetrapods. These fish may live on land, breathing air and being propelled by their pelvic fins. Australia has three populations of the few remaining lungfish — two marine populations and one inhabiting the Mary River basin in Queensland.

Hence, tetrapods are most common ancestors with lung fish.

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.