Which of the following BEST explains the timing of the classical pathway of complement fixation, relative to the other pathways of complement fixation, against a pathogen in an individual who hasnever been exposed to said pathogen?

A. No target for C1qrs exists on the surface of the pathogen in the earliest stages of theresponse to it.

B. The chemical environment of the pathogen's surface favors the spontaneous activation ofsoluble C3 immediately upon exposure to the pathogen.

C. C1qrs immediately recognizes carbohydrate antigens on the surface of the pathogen, allowing for rapid formation of the C4b2a C3 convertase.

D. The pathogen expresses one or more factors on its surface that act as negative regulators ofC3 convertase formation.

E. None of the above

A

Explanation:

1. There are 3 pathways of complement activation:

i) the classical pathway;

ii) the MB-lectin pathway; and

iii) the alternative pathway.

2. The classical complement pathway;  for activation, it requires antigen(Ag) antibody(Ab) complexes.

3. While the other pathways can be activated by various ways.

as here,  No target for C1qrs exists on the surface of the pathogen in the earliest stages of the response to it.

Science27 of the most iconic, jaw-dropping photos of the earth and the moon from spacedave mosher  oct 1, 2018, 11: 13 am etnasa/flickrapollo 11 astronauts took this photo of earth on july 20, 1969.from the ground, earth looks like a boundless fertile plain that beckons to be explored and exploited.but astronauts would beg -  and even plead  - to differ."you realize that people often say, 'i hope to go to heaven when i die,'" jim lovell, an astronaut who flew on the apollo 8 and apollo 13 missions to the moon, previously  told business insider. "in reality, if you think about it, you go to heaven when you're born."lovell has seen first-hand that we live on a tiny rock hopelessly lost in the void. he's also quick to tell you it's the only one we've got - a  fragile spaceship  for more than 7 billion people: "you arrive on a planet that has the proper mass, has the gravity to contain water and an atmosphere, which are the very essentials for life. and you arrive on this planet that's orbiting a star just at the right distance - not too far to be too cold, or too close to be too hot - and just at the right distance to absorb that star's energy and then, with that energy, cause life to evolve here in the first place. in reality, you know, god has really given us a stage, just looking at where we were around the moon, a stage on which we perform. and how that play turns out is up to us, i guess."humanity has recorded photos of earth from hundreds, thousands, millions, and even billions of miles away, some of them taken by lovell himself.these images not only scientists study our dynamic world, but also understand how a habitable planet looks from afar, which aids the search for  more worlds. most importantly, however, the images underscore our peculiar existence on  a mote of cosmic dust.take a moment to ponder 27 of the most arresting images of earth that humankind has ever captured from space.a